Journal articles on the topic 'Geometric solid modelling'
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1
Bates, J. P., A. J. Morris, and P. N. Payne. "Knowledge-based geometric modelling of aircraft structures." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 211, no. 4 (April 1, 1997): 273–84. http://dx.doi.org/10.1243/0954410971532677.
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Aerospace engineering offers a challenging test environment for advanced design systems and methods. Focusing particularly on knowledge-based engineering (KBE) systems, this paper demonstrates their application in automating the solid modelling of aircraft structures. The principles are illustrated through a case study example in which a description is given of the knowledge-based geometric modelling of light alloy fuselage frame sectors. The business benefits of using KBE systems in an aerospace engineering programme are quantified. Recommendations for the extended application of the technology to achieve strategic market advantage are also given.
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Stobart, R. K. "Geometric tools for the off-line programming of robots." Robotica 5, no. 4 (October 1987): 273–80. http://dx.doi.org/10.1017/s0263574700016295.
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SUMMARYOff-line programming of robots has a number of clear advantages over traditional ‘teach1’ methods which require the robot to be taken out of production. However, off-line programming techniques require extensive geometric facilities which are ideally provided by a geometric modelling system.The use of modelling covers the planning of the robot workcell, as well as the detailed planning of the robot operations. Assembly, in particular, requires detailed geometric information concerning geometric features and solid properties.
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Al Qahtani, Waleed M. S., Salah A. Yousief, and Mohamed I. El-Anwar. "Recent Advances in Material and Geometrical Modelling in Dental Applications." Open Access Macedonian Journal of Medical Sciences 6, no. 6 (June 17, 2018): 1138–44. http://dx.doi.org/10.3889/oamjms.2018.254.
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This article touched, in brief, the recent advances in dental materials and geometric modelling in dental applications. Most common categories of dental materials as metallic alloys, composites, ceramics and nanomaterials were briefly demonstrated. Nanotechnology improved the quality of dental biomaterials. This new technology improves many existing materials properties, also, to introduce new materials with superior properties that covered a wide range of applications in dentistry. Geometric modelling was discussed as a concept and examples within this article. The geometric modelling with engineering Computer-Aided-Design (CAD) system(s) is highly satisfactory for further analysis or Computer-Aided-Manufacturing (CAM) processes. The geometric modelling extracted from Computed-Tomography (CT) images (or its similar techniques) for the sake of CAM also reached a sufficient level of accuracy, while, obtaining efficient solid modelling without huge efforts on body surfaces, faces, and gaps healing is still doubtable. This article is merely a compilation of knowledge learned from lectures, workshops, books, and journal articles, articles from the internet, dental forum, and scientific groups' discussions.
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Lámer, Géza. "Continuous and discrete models in the mechanics of deformable solid bodies." MATEC Web of Conferences 184 (2018): 01004. http://dx.doi.org/10.1051/matecconf/201818401004.
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The study provides an overview of modelling possibilities for the mechanical behaviour of media. The discrete, continuous or differential geometric as well as the discrete nature and continuous description grid continuum model in particular are highlighted. We point out that the differential geometric model is based on the concept of continuity and interprets a continuous medium model. We reveal that the grid continuum model is based on the application of numerical method and interprets a discrete medium model.
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Chieslar, J. D., and A. Ghali. "Solid to shell element geometric transformation." Computers & Structures 25, no. 3 (January 1987): 451–55. http://dx.doi.org/10.1016/0045-7949(87)90136-2.
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Baldwin, A. T., and M. M. Rashid. "A geometric model of decohesion in solid continua." International Journal of Fracture 180, no. 2 (February 5, 2013): 205–21. http://dx.doi.org/10.1007/s10704-013-9811-x.
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Łukaszewicz, Andrzej, and Kanstantsin Miatliuk. "Reverse Engineering Approach for Object with Free-Form Surfaces Using Standard Surface-Solid Parametric CAD System." Solid State Phenomena 147-149 (January 2009): 706–11. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.706.
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In this paper the reverse modelling process for mapping and reconstructing the geometric characteristics of element with free-form surfaces as virtual CAD model is described. The basic approach in reverse modelling process in middle range standard parametric 3D modeler such as SolidWorks system is presented. The digitizing process was performed on the coordinate measuring machine. Using surface-solid modelling tools the virtual solid models were created. They are based on prepareing 3D curves from cloud of points as a sectional profiles. As the next step, it is possible to realize various CAx applications based on 3D feature-based model. In our case an abrasive wear of rotor blade was estimated.
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Biradar, Rohitkumar S. "Finite Element Modelling and Analysis of Pressure Vessel." International Journal for Research in Applied Science and Engineering Technology 10, no. 9 (September 30, 2022): 910–14. http://dx.doi.org/10.22214/ijraset.2022.46770.
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Abstract: In recent years, most of the sectors replace conventional materials with aluminium matrix materials. Various mechanical studies have been done, such as tensile, impact, flexural, and hardness. For the same geometrical parameters of the steel pressure vessel, FE Analysis of Structural Steel pressure vessel is carried out, and stresses for internal pressures are determined. And the Geometric Modelling is carried out in design software solid works and analyse in ANSYS workbench. The Structural analysis of pressure vessel was carried out. The validation for Hoop stress, Longitudinal stress& Maximum shear stress was done. Cylindrical pressure vessels are widely used for commercial, under water vehicles and in aerospace applications. And the Geometric Modelling is carried out in solid works. And analysed in ANSYS Workbench. The Comparison has done between FEM results and Theoretical results for Validation purposes. The Calculations for Hoop Stress, Longitudinal Stress & Maximum Shear Stress was Calculated for theoretical. The boundary conditions and dimensions for Modelling of a Pressure vessel was taken from the paper and same Boundary conditions was applied for analysis purposes. For Structural steel the design is safe because the stress value is within range of yield strength. The Material properties used are structural properties of steel for the analysis Purposes.
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Ikeuchi, Daiki, Alejandro Vargas-Uscategui, Xiaofeng Wu, and Peter C. King. "Neural Network Modelling of Track Profile in Cold Spray Additive Manufacturing." Materials 12, no. 17 (September 2, 2019): 2827. http://dx.doi.org/10.3390/ma12172827.
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Cold spray additive manufacturing is an emerging technology that offers the ability to deposit oxygen-sensitive materials and to manufacture large components in the solid state. For further development of the technology, the geometric control of cold sprayed components is fundamental but not yet fully matured. This study presents a neural network predictive modelling of a single-track profile in cold spray additive manufacturing to address the problem. In contrast to previous studies focusing only on key geometric feature predictions, the neural network model was employed to demonstrate its capability of predicting complete track profiles at both normal and off-normal spray angles, resulting in a mean absolute error of 8.3%. We also compared the track profile modelling results against the previously proposed Gaussian model and showed that the neural network model provided comparable predictive accuracy, even outperforming in the predictions at cold spray profile edges. The results indicate that a neural network modelling approach is well suited to cold spray profile prediction and may be used to improve geometric control during additive manufacturing with an appropriate process planning algorithm.
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Fan, Jun. "Computer Data Structure for Geological Entities Modelling Based on OO-Solid Model." Advanced Materials Research 383-390 (November 2011): 2484–91. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.2484.
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In the long evolution of the earth formation often form a complex geological structure, modeling for these complex geological entities (such as thinning-out, bifurcation, reverse, etc.) still require in-depth 3D modeling study. Because of discontinuity, complexity and uncertainty of distribution of 3D geo-objects, some models only are suitable for regular, continuous and relatively simple spatial objects, and some are suitable for discontinue, complex and uncertain geo-objects, but some improvements on these models, such as, updating of model, maintenance of topological and seamless integration between models, are still to be made. OO-Solid model, put forward by writer in 2002, is an object- oriented topological model based on sections. The OO-Solid Model is an object-oriented 3D topologic data model based on component for geology modeling with fully considering the topological relations between geological objects and its geometric primitives, Comparatively, it accords with the actual requirements of three-dimensional geological modeling . The key issue of 3D geology modeling is the 3D data model. Some data models are suitable for discontinue, complex and uncertain geo-objects, but the OO-Solid model is an object-oriented 3D topologic data model based on component for geology modeling with fully considering the topological relations between geological objects and its geometric primitives. OO-Solid model and data structure are designed. At last, 3D complex geological entities modeling based on OO-Solid are studied in this paper. These study is important and one of the core techniques for the 3DGM.
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Williams, G. J., Y. K. Chen, and F. S. Bhinde. "Modelling of a Monolithic Solid Oxide Fuel Cell." Advanced Materials Research 750-752 (August 2013): 1718–33. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.1718.
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The paper presents a bespoke mathematical model that simulates the electrochemical, thermal and fluid-dynamic interactions in a solid oxide fuel cell. This model is created for the purpose of evaluating and optimising a novel SOFC architecture. The proprietary fuel cell design consists of cathode supported cross-flow monolithic flow channels of hexagonal honeycomb section. The monolithic cells are constructed from porous cathodic material, with porous anodic and dense electrolytic material deposited inside specific hexagons such that any anodic cell is surrounded by six cathodic cells. Current collection is achieved by bus-plating on the monolith perpendicular to the direction of flow, and using thin interconnects attached to a corner of an anodic cell. The mathematical model considers a single side of the hexagon to simulate electrochemical interactions combined with heat and mass transfer. The finite difference technique is applied to predict numerically from a given current value voltage potential, temperature, fuel and oxidant compositions and partial pressures at the electrolyte/electrode interfaces. The model can be treated as a small segment of any geometry, thus can be, with added complexities of non-uniformity in surface thickness, extended to other shapes, and therefore used as an aid at the design stage to choose the values of geometric variables such as electrode and electrolyte thickness, etc.
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Boryga, Marek, and Paweł Kołodziej. "Numerical verification of the correctness of the modelling clutch with adjustable torsional." Mechanik 91, no. 10 (October 8, 2018): 838–41. http://dx.doi.org/10.17814/mechanik.2018.10.139.
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Construction, principles and results of stress analysis and modal analysis of the clutch components with adjustable torsional flexibility are presented. Solid models of individual elements, geometric relations between them, stress analysis and modal analysis were made using the Autodesk Inventor program. Results of the analysis confirm the correctness of the clutch construction in terms of mechanical properties.
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Davy, J. R., and P. M. Dew. "A polymorphic library for constructive solid geometry." Journal of Functional Programming 5, no. 3 (July 1995): 415–42. http://dx.doi.org/10.1017/s0956796800001416.
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AbstractSolid modelling using constructive solid geometry (CSG) includes many examples of stylised divide-and-conquer algorithms. We identify the sources of these recurrent patterns and describe a Geometric Evaluation Library (GEL) which captures them as higher-order functions. This library then becomes the basis of developing CSG applications quickly and concisely. GEL is currently implemented as a set of separately compiled modules in the pure functional language Hope+. We evaluate our work in terms of performance and general applicability. We also assess the benefits of the functional paradigm in this domain and the merits of programming with a set of higher-order functions.
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Sakkalis, T., G. Shen, and N. M. Patrikalakis. "Topological and Geometric Properties of Interval Solid Models." Graphical Models 63, no. 3 (May 2001): 163–75. http://dx.doi.org/10.1006/gmod.2001.0539.
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Stasinopoulos, Thanos N. "A SURVEY OF SOLAR ENVELOPE PROPERTIES USING SOLID MODELLING." Journal of Green Building 13, no. 1 (January 2018): 3–30. http://dx.doi.org/10.3992/1943-4618.13.1.3.
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Solar envelope is a concept for regulating solar access in urban planning. It is a roof-like imaginary surface over a given piece of land that controls the maximum allowed building height in order to avoid casting shadows on the neighbours during a specific period. The volume of solar envelopes regulates building density, depending on geometric attributes and time (plot size and proportions, orientation, ground slope, latitude, duration of insolation). This work compares the effect of such factors on the size of solar envelopes on a variety of land parcels, individually or in groups. Repeated applications of solid modelling are used to calculate in each case the values of ‘Solar Volume Coefficient’, i.e. the volume of a solar envelope per unit of its base as a measure for comparisons. Results show the influence of the various factors affecting the geometry of solar envelopes. Among other findings, it is also shown that solar envelopes generate urban densities lower than conventional urban regulations. The total volume of solar envelopes over an area ( ‘Solar Building Potential’) can be increased by raising the reference level of solar envelopes ( ‘shadow fence’ or ‘solar fence’). Lower urban densities are compensated by facilitating solar applications, as well as by enhancing daylight, ventilation, and vistas in the urban context, thus creating new ‘solar cityscapes’ exemplified here on existing street patterns.
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Luis Pérez, C. J., J. Vivancos Calvet, and M. A. Sebastián Pérez. "Geometric roughness analysis in solid free-form manufacturing processes." Journal of Materials Processing Technology 119, no. 1-3 (December 2001): 52–57. http://dx.doi.org/10.1016/s0924-0136(01)00897-4.
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Большаков, V. Bolshakov, Чагина, and A. Chagina. "Test Tasks on Bases of 3D-Modelling." Geometry & Graphics 4, no. 4 (December 19, 2016): 60–68. http://dx.doi.org/10.12737/22844.
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At the beginning of this paper a short review of known
geometric and graphic tests has been presented, and a practical lack of
test tasks on computer graphics tools application for geometrical simulation
problems solution has been emphasized. The test tasks directed
to assessment the level of intellectual abilities related to the optimum
choice of solid-state simulation tools for creation and editing products’
parametrical sketches and models in the KOMPAS-3D system are offered.
The content of the developed test tasks is based on analysis of 3D
simulation’s stages within which novice users allow maximum number
of wrong or far from optimum actions. In the test task on rational construction
of parametrical sketches it is necessary to choose commands
from the submitted lists for creation of the shown sketches. Tasks on
solid-state simulation for details are based on the analysis of a form of
fifteen models shown in axonometric projections. It is offered to optimize
simulation procedures and to specify a minimum number of forming
operations for creation of shown details models. Tasks on solid-state
models editing show a multivariance of procedures for models creation
and editing; these tasks have been directed to the rational choice for the
minimum number of the forming operations for models modification.
In a task on kinds insert in an associative drawing it is offered to make
for the details shown in axonometry a right choice on number and
content of necessary images in the associative drawing. In a test task on
solid-state simulation for two-component assembly units is required to
choose from a presented set of separate components the ones which are
necessary for subsequent mental conjunction by executing the command
“components’ side coincidence”.
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Biljecki, F., H. Ledoux, X. Du, J. Stoter, K. H. Soon, and V. H. S. Khoo. "THE MOST COMMON GEOMETRIC AND SEMANTIC ERRORS IN CITYGML DATASETS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W1 (October 5, 2016): 13–22. http://dx.doi.org/10.5194/isprs-annals-iv-2-w1-13-2016.
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To be used as input in most simulation and modelling software, 3D city models should be geometrically and topologically valid, and semantically rich. We investigate in this paper what is the quality of currently available CityGML datasets, i.e. we validate the geometry/topology of the 3D primitives (Solid and MultiSurface), and we validate whether the semantics of the boundary surfaces of buildings is correct or not. We have analysed all the CityGML datasets we could find, both from portals of cities and on different websites, plus a few that were made available to us. We have thus validated 40M surfaces in 16M 3D primitives and 3.6M buildings found in 37 CityGML datasets originating from 9 countries, and produced by several companies with diverse software and acquisition techniques. The results indicate that CityGML datasets without errors are rare, and those that are nearly valid are mostly simple LOD1 models. We report on the most common errors we have found, and analyse them. One main observation is that many of these errors could be automatically fixed or prevented with simple modifications to the modelling software. Our principal aim is to highlight the most common errors so that these are not repeated in the future. We hope that our paper and the open-source software we have developed will help raise awareness for data quality among data providers and 3D GIS software producers.
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Olimpia Pavlov, Ştefu, Constantin Dogariu, and Elena Savu. "Techniques for the Modelling and Control of Cutting Tools by the Use of 3D Scanners and CAD Programmes." Applied Mechanics and Materials 835 (May 2016): 705–11. http://dx.doi.org/10.4028/www.scientific.net/amm.835.705.
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The paper presents the bases of a methodology for obtaining a 3D solid model by three-dimensional scanning. The three-dimensional scanning has been available for more than 15 years; and yet, some people have heard of it but a few are familiar with the applications of this technology. 3D scanning is also known as 3D digitization, its name coming from the fact that it is a process that employs a contact or non-contact digitizing feeler in order to capture the form of objects and recreate them as 3D graphic representations in a virtual work space through a very dense network of points (xyz). By means of certain specialized programmes, we can obtain not only the tool’s geometric parameters that can be compared with the obligatory parameters, but also a direct evaluation of the geometric deviations from ideal values.
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Alpatov, Vadim. "Building constructions modelling problems in modern cae-systems." E3S Web of Conferences 135 (2019): 03066. http://dx.doi.org/10.1051/e3sconf/201913503066.
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This article is about choosing building structure analysis model question. Construction analysis model type choice affects result of counting. Result accuracy and reliability depends on analysis scheme choice. Using modern computers, there is a lot of alternative abilities of creation construction analysis model. This article is made to understand these analysis models features and their influence on result. An example of counting beam in six independent CAD systems is shown. Engineering simulation and design software, which base on finite elements method, were chosen for analysis. These counting models differ from each other only by geometrical scheme. Beam geometry modeling is performed using beam elements, shell elements and solid elements. The comparison of beam calculation results with its beam, shell and solid elements analysis scheme modelling was performed. The analysis of single factor (geometric scheme) influence on the results of beam calculation is shown. It was defined, that the choice of calculation complex does not affect the calculation result, if the geometrical counting models are completely identical. It was defined, that in case creating construction with various types finite elements there are differences in the calculation results. Difference in calculation results, using different geometrical models, is seen in using the same complex and in comparison of different complexes. It was defined, that difference in calculating internal forces and moments in beam for different geometrical models can be more than 10%.
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Jindra, Daniel, Zdeněk Kala, and Jiří Kala. "A Comparison of Shell and Solid Finite Element Models of Austenitic Stainless Steel Columns in Compression." IOP Conference Series: Materials Science and Engineering 1203, no. 3 (November 1, 2021): 032048. http://dx.doi.org/10.1088/1757-899x/1203/3/032048.
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Abstract The subject of this article is the implementation of new knowledge on material and geometric characteristics obtained from an experimental research program in advanced numerical modelling of compressed columns made of austenitic stainless steel using the ANSYS Classic software. Nonlinear stress–strain curves were obtained using our own experimental program and studied in terms of identifying the most suitable nonlinear material model. Additional material and geometric characteristics were obtained from literature and other independent research. Numerical models differing in mesh density localization, formulation of element integration, non-linear material model, and initial geometric imperfections were created and compared. The aim of the models was the ultimate limit state of a strut of circular hollow cross-section stressed by compression and analysed using the geometrically and materially nonlinear solution with consideration to the influence of initial imperfections. Static resistance and limit state deformations are compared for each model. The paper presents the analysis of model uncertainty by comparing SHELL and SOLID FE models, which must be characterized before the start of the analysis of the random influence of imperfections on the limit states. The mean values and the coefficients of variation are practically the same for both approaches. In summary, the presented models can be considered sufficiently validated and eligible for integration in tandem with simulation sampling methods.
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Yang, X., M. Koehl, and P. Grussenmeyer. "MESH-TO-BIM: FROM SEGMENTED MESH ELEMENTS TO BIM MODEL WITH LIMITED PARAMETERS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2 (May 30, 2018): 1213–18. http://dx.doi.org/10.5194/isprs-archives-xlii-2-1213-2018.
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Building Information Modelling (BIM) technique has been widely utilized in heritage documentation and comes to a general term Historical/Heritage BIM (HBIM). The current HBIM project mostly employs the scan-to-BIM process to manually create the geometric model from the point cloud. This paper explains how it is possible to shape from the mesh geometry with reduced human involvement during the modelling process. Aiming at unbuilt heritage, two case studies are handled in this study, including a ruined Roman stone architectural and a severely damaged abbey. The pipeline consists of solid element modelling based on documentation data using <i>Autodesk Revit</i>, a common BIM platform, and the successive modelling from these geometric primitives using <i>Autodesk Dynamo</i>, a visual programming built-in plugin tool in <i>Revit</i>. The BIM-based reconstruction enriches the classic visual model from computer graphics approaches with measurement, semantic and additional information. <i>Dynamo</i> is used to develop a semi-automated function to reduce the manual process, which builds the final BIM model from segmented parametric elements directly. The level of detail (LoD) of the final models is dramatically relevant with the manual involvement in the element creation. The proposed outline also presents two potential issues in the ongoing work: combining the ontology semantics with the parametric BIM model, and introducing the proposed pipeline into the as-built HBIM process.
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Arthurs, Christopher J., Rostislav Khlebnikov, Alex Melville, Marija Marčan, Alberto Gomez, Desmond Dillon-Murphy, Federica Cuomo, et al. "CRIMSON: An open-source software framework for cardiovascular integrated modelling and simulation." PLOS Computational Biology 17, no. 5 (May 10, 2021): e1008881. http://dx.doi.org/10.1371/journal.pcbi.1008881.
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In this work, we describe the CRIMSON (CardiovasculaR Integrated Modelling and SimulatiON) software environment. CRIMSON provides a powerful, customizable and user-friendly system for performing three-dimensional and reduced-order computational haemodynamics studies via a pipeline which involves: 1) segmenting vascular structures from medical images; 2) constructing analytic arterial and venous geometric models; 3) performing finite element mesh generation; 4) designing, and 5) applying boundary conditions; 6) running incompressible Navier-Stokes simulations of blood flow with fluid-structure interaction capabilities; and 7) post-processing and visualizing the results, including velocity, pressure and wall shear stress fields. A key aim of CRIMSON is to create a software environment that makes powerful computational haemodynamics tools accessible to a wide audience, including clinicians and students, both within our research laboratories and throughout the community. The overall philosophy is to leverage best-in-class open source standards for medical image processing, parallel flow computation, geometric solid modelling, data assimilation, and mesh generation. It is actively used by researchers in Europe, North and South America, Asia, and Australia. It has been applied to numerous clinical problems; we illustrate applications of CRIMSON to real-world problems using examples ranging from pre-operative surgical planning to medical device design optimization.
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Mounayri, H. El, A. D. Spence, and M. A. Elbestawi. "Milling Process Simulation—A Generic Solid Modeller Based Paradigm." Journal of Manufacturing Science and Engineering 120, no. 2 (May 1, 1998): 213–21. http://dx.doi.org/10.1115/1.2830116.
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A generic solid modeller based milling process simulation system is developed for 3-axis milling of complex parts. Parts are described using a boundary representation solid model, and cutting edges are fitted with cubic Be´zier curves. For every completed tool path (i.e., one NC block), the tool swept volume is generated and intersected with the part, yielding the corresponding removed material volume. The tool cutting edges are then intersected with that volume to produce the tool-part immersion geometry. The mechanistic milling process model produces an accurate simulation of cutting forces, torque and power. Modelling of tool and tool holder dynamics is included. The system is based on a generic procedure for extracting geometric data required to accurately simulate milling of complex parts. Any tool shape can be represented, and extension to 4- and 5-axis machining is straightforward. Related processes such as turning and drilling can be modelled in a similar way. The capability of the system is demonstrated experimentally for ball end milling.
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Barrera Vera, José Antonio, Antonio Pérez Romero, Rafael Ortiz Marín, and Carlos Cobos Gutiérrez. "Nuevas tecnologías en levantamientos aplicadas a la restauración: “El Giraldillo’’." Virtual Archaeology Review 2, no. 3 (April 15, 2011): 115. http://dx.doi.org/10.4995/var.2011.4628.
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<p>This work consists in the geometric survey of a big statue by means of a laser scanner and solid modelling. It has been chosen, for its complexity and singularity of the image. It’s about the copy of the weather vane that crowns the tower of the Giralda of Seville, the well-known " Giraldillo ", carried out by traditional methods a few years ago. The big dimensions of the study object and its location in a public place make that other methods of obtaining of data cannot be applied without using auxiliary elements to be carried out, this would suppose to have disable its exhibition during a certain time.</p><p>By means of this experience we will have opportunity to contrast the results of the application of technical of geometric survey with laser total station and threedimensional laser scanner.</p>
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Meftah, Kamel, Lakhdar Sedira, and Ayoub Ayadi. "A six-node prismatic solid finite element for geometric nonlinear problems in elasticity." Mathematics and Computers in Simulation 182 (April 2021): 143–64. http://dx.doi.org/10.1016/j.matcom.2020.10.021.
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Lai, T.-S. "Geometric design of a pinion with two circularly arrayed conical teeth for roller drives." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 220, no. 9 (September 1, 2006): 1405–12. http://dx.doi.org/10.1243/09544062jmes175.
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This article presents a mathematical model and geometric design algorithm for a new type of roller drive. The pinion has conical teeth in two circular arrays instead of one. This work is based on coordinate transformation and envelope theory, from which the equation of meshing of the cycloid drive is derived. The pinion profiles are the equidistant curves of the epicycloid profiles except the contour of the pinion conical tooth holes. Although there are twice as many pinion teeth as conventional rollers, their speed ratios are identical. This approach can design roller drives in which the pinion has two circular arrays of conical and cylindrical rollers. On the basis of these results, the corresponding solid modelling is constructed by CAD. Four examples are presented to demonstrate the feasibility of this approach. These examples can be a useful reference as a design case for other tooth profiles.
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Nearchou, Antony, Mero-Lee Cornelius, Jonathan Skelton, Zöe Jones, Andrew Cairns, Ines Collings, Paul Raithby, Stephen Wells, and Asel Sartbaeva. "Intrinsic Flexibility of the EMT Zeolite Framework under Pressure." Molecules 24, no. 3 (February 12, 2019): 641. http://dx.doi.org/10.3390/molecules24030641.
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The roles of organic additives in the assembly and crystallisation of zeolites are still not fully understood. This is important when attempting to prepare novel frameworks to produce new zeolites. We consider 18-crown-6 ether (18C6) as an additive, which has previously been shown to differentiate between the zeolite EMC-2 (EMT) and faujasite (FAU) frameworks. However, it is unclear whether this distinction is dictated by influences on the metastable free-energy landscape or geometric templating. Using high-pressure synchrotron X-ray diffraction, we have observed that the presence of 18C6 does not impact the EMT framework flexibility—agreeing with our previous geometric simulations and suggesting that 18C6 does not behave as a geometric template. This was further studied by computational modelling using solid-state density-functional theory and lattice dynamics calculations. It is shown that the lattice energy of FAU is lower than EMT, but is strongly impacted by the presence of solvent/guest molecules in the framework. Furthermore, the EMT topology possesses a greater vibrational entropy and is stabilised by free energy at a finite temperature. Overall, these findings demonstrate that the role of the 18C6 additive is to influence the free energy of crystallisation to assemble the EMT framework as opposed to FAU.
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Kalmykova, Svitlana. "SIMULATION OF T-JOINTS BETWEEN RHS STEEL MEMBERS WITH OFFSET IN ABAQUS CAE." Acta Polytechnica CTU Proceedings 30 (April 22, 2021): 36–40. http://dx.doi.org/10.14311/app.2021.30.0036.
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The current paper focuses on numerical simulation peculiarities of offset welded rectangular hollow section joints. Understanding the modelling techniques can result in easier and faster and above all correct outcomes from FEA for future use. The steel joints under discussion are composed from cold-formed regular rectangular hollow sections where RHS brace members are laterally shifted from chord axis. Joints work under monotonically increasing compression load applied to a brace top. Numerical models were developed in FE programme Abaqus. FE-models is composed of C3D8R 8-noded solid linear brick elements with an emphasis on mesh size effect and modelling of a weld seam. FE advanced model were compiled considering both material and geometric nonlinearities. For validation purposes, the full-scale laboratory tests were conducted. Proposed FE models reliably predict the structural behaviour of welded offset T-joints thanks to good agreement achieved on deformation limit 3 % b0 with the maximum deviation 10.3 %.
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Armasoiu, Giorgiana Elena. "Accurate NC Program Generation Based on New Model Editing Process." Applied Mechanics and Materials 809-810 (November 2015): 805–10. http://dx.doi.org/10.4028/www.scientific.net/amm.809-810.805.
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This paper emphasizes the benefits of part-model editing process that does not depend on hystory-based modelling system. The use of synchronous technology in mechanical engineering applications allows the NC programmer to efficiently generate the NC program regardless the source of 3D model. The programming and machining process can be more efficient if the intuitive geometric changes on 3D model are allowed. Synchronous technology makes possible NC programmer’s intervention over 3D model geometry, without breaking the rules defined in CAD. Synchronous technology works with both, native and non-native models and it is available in NX and Solid Edge. With synchronous technology, the changes are performed with or without regard to the history of the model.
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Tai, Y. C., and C. Y. Kuo. "Modelling shallow debris flows of the Coulomb-mixture type over temporally varying topography." Natural Hazards and Earth System Sciences 12, no. 2 (February 6, 2012): 269–80. http://dx.doi.org/10.5194/nhess-12-269-2012.
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Abstract. We propose a saturated binary mixture model for debris flows of the Coulomb-mixture type over temporally varying topography, where the effects of erosion and deposition are considered. Due to the deposition or erosion processes, the interface between the moving material and the stagnant base is a non-material singular surface. The motion of this singular surface is determined by the mass exchange between the flowing layer and the ground. The ratio of the relative velocity between the two constituents to the velocity of the solid phase is assumed to be small, so that the governing equations can be reduced to a system of the quasi-single-phase type. A shock-capturing numerical scheme is implemented to solve the derived equation system. The deposition shapes of a finite mass sliding down an inclined planary chute are investigated for a range of mixture ratios. The geometric evolution of the deposition is presented, which allows the possibility of mimicking the development of levee deposition.
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Du, Shenglan, Roderik Lindenbergh, Hugo Ledoux, Jantien Stoter, and Liangliang Nan. "AdTree: Accurate, Detailed, and Automatic Modelling of Laser-Scanned Trees." Remote Sensing 11, no. 18 (September 4, 2019): 2074. http://dx.doi.org/10.3390/rs11182074.
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Laser scanning is an effective tool for acquiring geometric attributes of trees and vegetation, which lays a solid foundation for 3-dimensional tree modelling. Existing studies on tree modelling from laser scanning data are vast. However, some works cannot guarantee sufficient modelling accuracy, while some other works are mainly rule-based and therefore highly depend on user inputs. In this paper, we propose a novel method to accurately and automatically reconstruct detailed 3D tree models from laser scans. We first extract an initial tree skeleton from the input point cloud by establishing a minimum spanning tree using the Dijkstra shortest-path algorithm. Then, the initial tree skeleton is pruned by iteratively removing redundant components. After that, an optimization-based approach is performed to fit a sequence of cylinders to approximate the geometry of the tree branches. Experiments on various types of trees from different data sources demonstrate the effectiveness and robustness of our method. The overall fitting error (i.e., the distance between the input points and the output model) is less than 10 cm. The reconstructed tree models can be further applied in the precise estimation of tree attributes, urban landscape visualization, etc. The source code of this work is freely available at https://github.com/tudelft3d/adtree.
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Yu, Dongling, Huiling Zhang, Jiangen Zhou, Lijun Deng, Dahai Liao, and Nanxing Wu. "Effect of geometric parameters at open turbine combined structure on flow field distribution of dry granulation for Si3N4 powder." International Journal of Modeling, Simulation, and Scientific Computing 12, no. 05 (March 26, 2021): 2150035. http://dx.doi.org/10.1142/s1793962321500355.
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To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbine combined structure on the flow field distribution is studied. The Euler–Euler gas-solid two-phase flow model is established and the physical model of dry granulation chamber under the combined structure is simplified. Under the same radial structure, the volume distribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by the CFD method. The influence of the axial structure at the open turbine on the flow field distribution of Si3N4 particles under different geometric parameters is compared. The results show that the axial structure of the open turbine in the granulation chamber is the most uniform when the number of blades is 6 and the inclination angle is [Formula: see text], and the circulating flow of the upper and lower parts of Si3N4 powder is strong.
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Gao, Wei Guo, Wen Tie Niu, and Da Wei Zhang. "Dynamic Flow Path Feature Based Hydraulic Manifold Block Design." Materials Science Forum 628-629 (August 2009): 275–80. http://dx.doi.org/10.4028/www.scientific.net/msf.628-629.275.
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The modelling method of dynamic flow path feature (DFPF) is proposed for the design process of hydraulic manifold block (HMB). In this method, temporary body model and B-Rep model are adopted to represent geometric model of DFPF; the former is used for showing flow path, checking connectivity and safe wall thickness, and the latter is used for saving the final results. A novel feature topological representation method based on solid adjacency graph (SAG) is provided, and then validity of feature semantics can be checked through SAG. Finally dynamic topological changeability of flow path feature is realized by constraint solution and knowledge driving. Object-oriented model of DFPF is given, and the design process of HMB based on DFPF is illustrated.
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Case, K., J. X. Gao, and N. N. Z. Gindy. "The Implementation of a Feature-Based Component Representation for CAD/CAM Integration." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 208, no. 1 (February 1994): 71–80. http://dx.doi.org/10.1243/pime_proc_1994_208_061_02.
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Recent research and development has the objective of increasing productivity and cost effectiveness by integrating many activities such as design, analysis, process planning, assembly planning and production planning which encompass the entire manufacturing planning and operational control aspects of a manufacturing enterprise. It has been recognized that a key to the integration lies in the determination of a representation scheme for products that can be interpreted for the various needs of these different applications. Geometric (solid) modellers were regarded by many researchers as the appropriate representation, but more recently a features approach has been proposed to enhance the capabilities of solid modellers. This paper introduces ongoing research which is aimed at the development of a feature-based design system for process planning. The system is fully integrated with a conventional boundary representation (Brep) modeller which enhances its modelling capabilities in representing, editing and validating features of components. The main aspects of the feature-based design system are described in detail, such as the feature library, feature taxonomy, feature operations, feature relationships and tolerances. The generation of a detailed data model for transmission to manufacturing planning activities is also described and demonstrated by reference to an example component. A brief indication is given of our parallel research work in using such models as the basis of process planning and process capability modelling.
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Chronopoulos, Dimitrios, Manuel Collet, and Mohamed Ichchou. "Wave sensitivity analysis for periodic and arbitrarily complex composite structures." Engineering Computations 34, no. 5 (July 3, 2017): 1572–97. http://dx.doi.org/10.1108/ec-06-2016-0200.
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Purpose This paper aims to present the development of a numerical continuum-discrete approach for computing the sensitivity of the waves propagating in periodic composite structures. The work can be directly used for evaluating the sensitivity of the structural dynamic performance with respect to geometric and layering structural modifications. Design/methodology/approach A structure of arbitrary layering and geometric complexity is modelled using solid finite element (FE). A generic expression for computing the variation of the mass and the stiffness matrices of the structure with respect to the material and geometric characteristics is hereby given. The sensitivity of the structural wave properties can thus be numerically determined by computing the variability of the corresponding eigenvalues for the resulting eigenproblem. The exhibited approach is validated against the finite difference method as well as analytical results. Findings An intense wavenumber dependence is observed for the sensitivity results of a sandwich structure. This exhibits the importance and potential of the presented tool with regard to the optimization of layered structures for specific applications. The model can also be used for computing the effect of the inclusion of smart layers such as auxetics and piezoelectrics. Originality/value The paper presents the first continuum-discrete approach specifically developed for accurately and efficiently computing the sensitivity of the wave propagation data for periodic composite structures irrespective of their size. The considered structure can be of arbitrary layering and material characteristics as FE modelling is used.
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Căpățână, G. F., and M. A. Potîrniche. "Aspects regarding 3d modelling and finite element analysis of a crusher bucket." IOP Conference Series: Materials Science and Engineering 1182, no. 1 (October 1, 2021): 012012. http://dx.doi.org/10.1088/1757-899x/1182/1/012012.
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Abstract The highest consumption of solid materials, especially rocks extracted from quarries, has the construction materials industry. These materials can be used either in natural form (gravel, sand), or after a reduced processing (marble, large stone, for foundations), or after a complex processing (lime, plaster, cement, sandstone, clay). The crusher buckets are used to grind materials in order to reach optimal or convenient sizes of processed materials in order to carry out a good technological process. The study of the shredding processes and of the equipment related to these processes is done in order to reduce the energy consumption necessary to reduce the dimensions of the raw materials to dimensions necessary for further processing. This study is of particular importance due to the fact that the shredding operation is energy intensive. This paper presents aspects regarding the geometric modelling of a crusher bucket and the finite element analysis of the bucket housing. All the components of the bucket were modelled in the Inventor software and then assembled to obtain the assembly. The modelling was based on an example of a crusher bucket taken from the literature. Finite element analysis was performed to highlight the eigenmodes of the crusher bucket in order to estimate the eigenfrequencies range of this equipment.
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Rausch, Sascha, Tobias Siebrecht, Petra Kersting, and Dirk Biermann. "Analysis and Simulation of Surface Topographies in Grinding of Thermally Sprayed Coatings." Advanced Materials Research 1018 (September 2014): 91–98. http://dx.doi.org/10.4028/www.scientific.net/amr.1018.91.
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The abrasive-wear resistance and the lifetime of tribologically stressed free-formed surfaces of forming tools can be increased by thermally sprayed tungsten carbide coatings. In order to improve the surface quality and the shape accuracy, the workpieces must be machined prior to industrial application. A suitable machining process is NC grinding on five-axis machining centres using abrasive mounted points. However, the high hardness of the applied coatings and the small diameter of the utilized tools pose a great challenge for the process design. In order to optimize the grinding process and predict the resulting surface topography, a geometric-kinematic simulation based on the modelling of individual grains using Constructive Solid Geometry techniques was developed. In this paper, the results of fundamental investigations on grinding tungsten carbide coatings and the developed process simulation are presented.
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FANG, LINCONG, DOMINIQUE MICHELUCCI, and SEBTI FOUFOU. "EQUATIONS AND INTERVAL COMPUTATIONS FOR SOME FRACTALS." Fractals 26, no. 04 (August 2018): 1850059. http://dx.doi.org/10.1142/s0218348x18500597.
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Very few characteristic functions, or equations, are reported so far for fractals. Such functions, called Rvachev functions in function-based modeling, are zero on the boundary, negative for inside points and positive for outside points. This paper proposes Rvachev functions for some classical fractals. These functions are convergent series, which are bounded with interval arithmetic and interval analysis in finite time. This permits to extend the Recursive Space Subdivision (RSS) method, which is classical in Computer Graphics (CG) and Interval Analysis, to fractal geometric sets. The newly proposed fractal functions can also be composed with classical Rvachev functions today routinely used in Constructive Solid Geometry (CSG) trees of CG or function-based modeling.
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Cipriani, L., J. García-León, and F. Fantini. "FROM THE GENERAL DOCUMENTATION OF HADRIAN'S VILLA TO DESIGN ANALYSIS OF COMPLEX CUPOLAS: A PROCEDURAL APPROACH." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W15 (August 21, 2019): 327–34. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w15-327-2019.
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<p><strong>Abstract.</strong> The paper illustrates the progress of Hadrian's Villa digital documentation with special emphasis on a series of modelling issues emerged while studying vaults and cupolas of the site. Together with the more general problem of giving scientific coherence to both active and passive sensor outputs – systematically gathered from 2013 – a methodological problem concerning data interpretation of complex <i>opus caementicium</i> vaults have become dramatically important for the interdisciplinary research team. A methodology for improving the understanding the original shapes of Hadrianic cupolas was designed to provide scholars and professionals operating at the Villa with reliable and easy to use outputs, for interpretation, restoration, maintenance practice. Sensors integration played a fundamental role since allowed researchers a global understanding of intrados and extrados surfaces using reverse modelling applications. Features and 2D primitives extracted from high-resolution models were analysed in order to create flexible procedural models of reconstruction hypothesis/completion of cupolas. Due to the very nature of these shapes (apparently irregular), but with a solid geometric conception, we applied the last achievements of Catmull-Clark bicubic surfaces in combination with Visual Programming Language (VPL).</p>
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Temme, F. P. "On spin irreps of (1 Ii 3) 12-fold uniform NMR spin systems as invariant-based dual tensorial sets: Roles in spin physics for weight sets and their -partitional frequency catalogues." Canadian Journal of Physics 80, no. 9 (September 1, 2002): 1069–83. http://dx.doi.org/10.1139/p02-005.
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A direct systematic approach is given to the derivation of outer M-labelled {|IM(.)>} dual (spin) irrep sets for identical n [Formula: see text] 12-fold higher Ii nuclear spin ensembles, stressing (i) the essential role of multipartite partitions in spin physics, (ii) the value of algorithmic tableaux-based decompositions in the subsequent [Formula: see text]n combinatorical modelling, and (iii) how the dual group invariants (based on time-reversal invariance) govern the auxiliary labels of specialized dual tensors. Such (uniform inner rank) dual group basis sets (spin representations) underlie both NMR and isotopomer CNP spectral weightings. Specific applications are discussed here to illustrate the value of number partitional-based designs for statistical frequencies and recent algorithmic "sst" ([Formula: see text]n)-encoding techniques in quantized spin physics of uniform higher spin sets. In addition, a democratic recoupled form of purely SU(2) × [Formula: see text]2n projective modelling for the dual group invariants (SI) is given via an augmented democratic form of Weyl time-reversal invariance (TRV), over some regular solid geometry. From simple lattice-point geometric constraints, a maximal (2n)-index limit is established for global NMR ensemble spin symmetry. PACS Nos.: 02.10De, 02.20-a, 05.36Ch, 11.30Er, 33.25+k, 33.20Vq
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Nguyen, Thanh Trung, and Buddhima Indraratna. "Hydraulic behaviour of parallel fibres under longitudinal flow: a numerical treatment." Canadian Geotechnical Journal 53, no. 7 (July 2016): 1081–92. http://dx.doi.org/10.1139/cgj-2015-0213.
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Modelling fluid flow through fibrous porous materials has gained increasing attention from industry and research communities. Analytical and numerical methods are commonly used to predict the hydraulic characteristics of fibrous material during fluid flow, although to date most techniques have been conducted using the same assumption that the geometric features of fibres remain unchanged. In other words, the mutual interaction between fibre elements and fluid is ignored, which undermines the actual working condition of fibres. This paper therefore presents a potential numerical approach that is capable of capturing the behaviour of a fluid–solid system. Individual fibres are simulated by the discrete element method (DEM) coupled with the concept of computational fluid dynamics (CFD), whereby the information contained in each phase is constantly exchanged and updated with other phases. In comparison with conventional solutions, including the Kozeny–Carman (K–C) fluid flow principle and other valid studies, the results show an acceptable agreement in predicting the hydraulic conductivity of a fibrous system. Subjected to laminar longitudinal flow, fibre motion is also evaluated with respect to varying bond stiffness and flow velocity. The study indicates the potential of the proposed technique in modelling drainage and filtration that is based on the hydraulic behaviour of fibrous porous geomaterials.
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Li, Yuan, and Bo Wu. "Relation-Constrained 3D Reconstruction of Buildings in Metropolitan Areas from Photogrammetric Point Clouds." Remote Sensing 13, no. 1 (January 1, 2021): 129. http://dx.doi.org/10.3390/rs13010129.
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The complexity and variety of buildings and the defects of point cloud data are the main challenges faced by 3D urban reconstruction from point clouds, especially in metropolitan areas. In this paper, we developed a method that embeds multiple relations into a procedural modelling process for the automatic 3D reconstruction of buildings from photogrammetric point clouds. First, a hybrid tree of constructive solid geometry and boundary representation (CSG-BRep) was built to decompose the building bounding space into multiple polyhedral cells based on geometric-relation constraints. The cells that approximate the shapes of buildings were then selected based on topological-relation constraints and geometric building models were generated using a reconstructing CSG-BRep tree. Finally, different parts of buildings were retrieved from the CSG-BRep trees, and specific surface types were recognized to convert the building models into the City Geography Markup Language (CityGML) format. The point clouds of 105 buildings in a metropolitan area in Hong Kong were used to evaluate the performance of the proposed method. Compared with two existing methods, the proposed method performed the best in terms of robustness, regularity, and topological correctness. The CityGML building models enriched with semantic information were also compared with the manually digitized ground truth, and the high level of consistency between the results suggested that the produced models will be useful in smart city applications.
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Mencías Carrizosa, David, Pepa Cassinello Plaza, and Ignacio Payá Zaforteza. "Principles and characteristics of CAD geometric modelling of historical buildings = Principios y características de los modelos geométricos CAD en edificios históricos." Building & Management 2, no. 1 (April 30, 2018): 3. http://dx.doi.org/10.20868/bma.2018.1.3685.
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The first and unavoidable phase in the intervention in the Heritage and the existing building is the realization of a survey. Currently, its purpose is to build a digital geometric model in a computer system that serves to represent the built object and also serve as a geometric basis for further analysis. This paper takes a tour of the models used in building the survey data and what input and output information they use. These models are reduced to point clouds, wired-frame and curves and surfaces models. Solid modelling (BIM) is not widespread in this field given the difficulties presented by its application. All of them have in common that they codify by means of a database that includes the points of the survey and in some occasions another additional database is necessary to complete the reconstruction of the f the geometric information. This information management allows the development of computer applications that automatically analyse existing constructions based on geometry, such as the verification of the equilibrium of masonry structures. This work allows, therefore, clarifying the field that connects the geometric modelling, analytical representation and computational techniques with the architectural survey and intervention in Heritage.ResumenLa intervención en el Patrimonio y la Edificación existente tiene como primera fase ineludible la realización de un levantamiento, cuya finalidad consiste, en la actualidad, en construir un modelo geométrico digital en un sistema informático que sirva para representar el bien construido y servir de base geométrica para análisis posteriores. Este trabajo realiza un recorrido por los modelos empleados en edificación histórica para determinar las técnicas de modelado que sirven para codificar dicha información y qué información de entrada y salida emplean. Estos modelos se reducen a nubes de puntos, alámbricos y curvas y superficies, ya que el modelado mediante sólidos (BIM) no se encuentra extendido en este campo dadas las dificultades que presenta su aplicación. Todos ellos tienen en común que se codifican mediante una base de datos que incluyen los puntos del levantamiento y en algunas ocasiones es necesario otra base de datos adicional para completar la reconstrucción de la información geométrica. La gestión de esta información permite desarrollar aplicaciones informáticas que, de manera automática, realicen análisis de las construcciones existentes basados en la geometría, como el caso de la verificación del equilibrio de estructuras de fábrica. Este trabajo permite, por tanto, clarificar el campo que conecta el modelado geométrico, la representación analítica y las técnicas computacionales con el levantamiento arquitectónico y la intervención en Patrimonio, y sirve de punto de partida para futuros desarrollos que permitan la gestión de la ingente cantidad de información que se genera en un levantamiento y puede ser empleada para entender el bien en el que se interviene.
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Wu, Qizhou, Jingjing Liu, Yong Jin, Youxing Chen, Lianxu Du, and L. M. Waqas. "Thickness measurement method for the thermal protection layer of a solid rocket motor based on a laser point cloud." Insight - Non-Destructive Testing and Condition Monitoring 64, no. 4 (April 1, 2022): 219–28. http://dx.doi.org/10.1784/insi.2022.64.4.219.
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The thermal protection layer of the solid rocket motor (SRM) is an important elastic material applied to the adhesive shell and propellant; the thickness of the layer is related to the performance of the SRM. This paper proposes a method of linear laser scanning to realise the precise thickness measurement of the thermal protection layer. The custom-designed data acquisition device separately collects distance values from the inner surface of the thermal protection layer, before and after coating, using a linear laser sensor. The two measured distance values are subtracted and D-H modelling (a classical kinematics modelling method proposed by Denavit and Hartenberg) is conducted, then the system errors are analysed and calibrated to obtain the 3D point cloud data of the profile. The iterative closest point (ICP) algorithm is used to register the point cloud data relating to the internal surface, then an octree-based simplification method is proposed to realise the denoising and simplification of the point cloud data. Next, the normal vector of the point cloud data is calculated and the reference surface is extracted as the projection plane. The simplified point cloud is then projected onto the plane and the geometric information of the point cloud data after projection is extracted. A series of distance differences, namely the thickness of the thermal protection layer, is obtained. Finally, the Poisson surface reconstruction algorithm is used to display the inner surface of the thermal protection layer. The results show that the difference between the calculated values and the measured values is less than 0.1 mm, indicating that the thickness of the thermal protection layer of the SRM can be measured by the proposed non-contact method.
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Sharma, G. K., and B. Gurumoorthy. "Modelling multiply connected heterogeneous objects using mixed-dimensional material reference features." Journal of Computational Design and Engineering 6, no. 3 (November 30, 2018): 337–47. http://dx.doi.org/10.1016/j.jcde.2018.11.003.
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Abstract This paper proposes a general method for ab-initio modelling and representation of heterogeneous objects that are associated with complex material variation over complex geometry. Heterogeneous objects like composites and naturally occurring objects (bones, rocks and meteorites) possess multiple and often conflicting properties (like high hardness and toughness simultaneously), which are associated with random and irregular material distribution. Modelling such objects is desired for numerical analysis and additive manufacturing to develop bio-implants, high-performance tools etc. However, it is difficult to define and map the arbitrary material distribution within the object as the material distribution can be independent of the shape parameters or form features used to construct its solid model. This paper represents the source of random and irregular material distribution by mixed-dimensional entities with a focus on modelling compositional heterogeneity. The domain of effect of each material reference entity is defined automatically by using Medial Axis Transform (MAT), where the material distribution can be intuitively prescribed, starting from the material reference entity and terminating at the medial axis segment bounding the corresponding domain. Within such a domain, the spatial variation of the material is captured by a distance field from the material reference entity, which can be controlled locally and independently. These domains are stored using the neighbourhood relation for efficient operations like altering material distribution across the material reference entity and material evaluation for a given geometric location. Results from an implementation for 2.5D objects are shown and the extension to 3D objects is discussed. Highlights Hybrid representation for complex heterogeneous objects. General method for ab-initio modelling of complex heterogeneous objects capture arbitrary material distribution by automatic domain decomposition. Local control of material composition through MAT around material feature. Specification of material composition without adding new entities to shape model.
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Lychev, S. A., T. N. Lycheva, and K. G. Koifman. "The Nonlinear evolutionary problem for self-stressed multilayered hyperelastic spherical bodies." PNRPU Mechanics Bulletin, no. 1 (December 15, 2020): 43–59. http://dx.doi.org/10.15593/perm.mech/2020.1.04.
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The present paper studies the evolutionary problem for self-stressed multilayered spherical shells. Their stress-strain state is characterized by incompatible local finite deformations that arise due to the geometric incompatibility of the stress-free shapes of the individual layers with each other. In the considered problem, these shapes are thin-walled hollow balls that cannot be assembled into a single solid without gaps or overlaps. Such an assembly is possible only with the preliminary deformations of individual layers, which cause self-balanced stresses in them. For multilayered structures with a large number of layers, a smoothing procedure is proposed, as a result of which the piecewise continuous functions defining the preliminary deformation of the layers are replaced by continuous distributions. The reference stress-free shape of a body constructed in this way is defined within the framework of geometric continuum mechanics as a manifold with a non-Euclidean (material) connection. For the problem in question, this connection is determined by the metric tensor and its deviation from the Euclidean connection is characterized by the scalar curvature. Generalized representations for Cauchy and Piola stresses are also obtained by the methods of geometric continuum mechanics. Computations, provided for the discrete structure and body with a non-Euclidean reference shape defined by the approximation of deformation parameters, numerically illustrate the convergency of the solution for the discrete model to corresponded solution for the continuous problem if the number of layers is increasing while their total thickness is constant. In modelling it is assumed that the material of the layers is compressible, homogeneous, hyperelastic, and determined by the first-order Mooney - Rivlin elastic potential. Individual layerwise finite deformations are supposed to be centrally symmetric.
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Zhou, G., Y. Huang, T. Yue, X. Li, W. Huang, C. He, and Z. Wu. "HYBRID MODELING BASED ON SCSG-BR AND ORTHOPHOTO." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3 (May 2, 2018): 2499–503. http://dx.doi.org/10.5194/isprs-archives-xlii-3-2499-2018.
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With the development of digital city, digital applications are more and more widespread, while the urban buildings are more complex. Therefore, establishing an effective data model is the key to express urban building models accurately. In addition, the combination of 3D building model and remote sensing data become a trend to build digital city there are a large amount of data resulting in data redundancy. In order to solve the limitation of single modelling of constructive solid geometry (CSG), this paper presents a mixed modelling method based on SCSG-BR for urban buildings representation. On one hand, the improved CSG method, which is called as “Spatial CSG (SCSG)” representation method, is used to represent the exterior shape of urban buildings. On the other hand, the boundary representation (BR) method represents the topological relationship between geometric elements of urban building, in which the textures is considered as the attribute data of the wall and the roof of urban building. What's more, the method combined file database and relational database is used to manage the data of three-dimensional building model, which can decrease the complex processes in texture mapping. During the data processing, the least-squares algorithm with constraints is used to orthogonalize the building polygons and adjust the polygons topology to ensure the accuracy of the modelling data. Finally, this paper matches the urban building model with the corresponding orthophoto. This paper selects data of Denver, Colorado, USA to establish urban building realistic model. The results show that the SCSG-BR method can represent the topological relations of building more precisely. The organization and management of urban building model data reduce the redundancy of data and improve modelling speed. The combination of orthophoto and urban building model further strengthens the application in view analysis and spatial query, which enhance the scope of digital city applications.
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Azzaz, Hamza, Djaffar Dahmoun, O. Chaterbache, and Mohammed Azzaz. "Prediction of Mechanical Properties of Coiled Carbon Nanotubes by Molecular Structural Mechanics Based Finite Element Modelling." Defect and Diffusion Forum 380 (November 2017): 124–34. http://dx.doi.org/10.4028/www.scientific.net/ddf.380.124.
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Carbon nanotubes (NTC) have very spectacular mechanical properties related to their nanometric structure, their perfect arrangement and their one-dimensional geometry. As with all materials, structural defects are inevitable and affects NTC properties. Among these defects, we distinguish the topological defects, the dislocations and the penta-hepta defect. But the presence of these defects is not totally harmful, because the existence of some structure like the coiled nanotube is the result of these defects. For this, in the first part of this work, the coiled carbon nanotube structure is studied, a method for the designing of this structure is proposed, the geometric parameters are detailed and the structural coefficients are determined. Therefore, a procedure for moving from a graphene sheet to a coiled nanotube is developed. Then, the second part of this study represents an attempt to calculate the spring constants of the spiral carbon nanotube. Mechanical properties of this material are investigated by means of molecular structural mechanics (MSM) method in ANSYS finite element code. The model serves as a link between the computational chemistry and the solid mechanics by substituting discrete molecular structures, with an equivalent-structural model. A coiled carbon nanotube has been modeled on the nanoscale by one-dimensional elements (3D beam). The results show a considerable influence of structural parameters (diameter, chirality, pitch and defect position) on the coiled nanotube mechanical properties.
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Gonizzi Barsanti, S., and G. Guidi. "A GEOMETRIC PROCESSING WORKFLOW FOR TRANSFORMING REALITY-BASED 3D MODELS IN VOLUMETRIC MESHES SUITABLE FOR FEA." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W3 (February 23, 2017): 331–38. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w3-331-2017.
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Conservation of Cultural Heritage is a key issue and structural changes and damages can influence the mechanical behaviour of artefacts and buildings. The use of Finite Elements Methods (FEM) for mechanical analysis is largely used in modelling stress behaviour. The typical workflow involves the use of CAD 3D models made by Non-Uniform Rational B-splines (NURBS) surfaces, representing the ideal shape of the object to be simulated. Nowadays, 3D documentation of CH has been widely developed through reality-based approaches, but the models are not suitable for a direct use in FEA: the mesh has in fact to be converted to volumetric, and the density has to be reduced since the computational complexity of a FEA grows exponentially with the number of nodes. <br><br> The focus of this paper is to present a new method aiming at generate the most accurate 3D representation of a real artefact from highly accurate 3D digital models derived from reality-based techniques, maintaining the accuracy of the high-resolution polygonal models in the solid ones. The approach proposed is based on a wise use of retopology procedures and a transformation of this model to a mathematical one made by NURBS surfaces suitable for being processed by volumetric meshers typically embedded in standard FEM packages. The strong simplification with little loss of consistency possible with the retopology step is used for maintaining as much coherence as possible between the original acquired mesh and the simplified model, creating in the meantime a topology that is more favourable for the automatic NURBS conversion.