1. Compression of triangulated solids’ surfaces by Decimating Reconstructable TrianglesBlaž Repnik, Borut Žalik, Krista Rizman Žalik, 2025, original scientific article Abstract: This paper introduces a new programming solution for reducing the size of files needed to store 3D geometric solids, whose surfaces are interpolated by watertight irregular triangle meshes. Unlike other approaches, the software does not introduce any special storage data format, but, instead, utilises popular CAD formats such as STL, OBJ, or PLY. This increases the software’s interoperability significantly. The software comprises an encoder and a decoder. The encoder estimates which facets may be removed in such a way that they can later be reconstructed unambiguously by the decoder. The decoder also ensures that the reconstructed triangles are oriented correctly. The encoder and the decoder are straightforward to understand and to implement. They are asymmetric, making any potential programming error easier to identify and correct.
Keywords: data compression, geometric modelling, computer-aided design, boundary representation, topology, watertightness
Published in DKUM: 30.05.2025; Views: 0; Downloads: 1
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2. Effect of topological optimisation on the kinetic properties of the kinematic chain : Elektronski virBoštjan Harl, 2025, original scientific article Abstract: The paper addresses the importance of topology and shape optimisation on improving the performance of a device operating in a mine industry. The process of increasing the stiffness and the value of the first eigenfrequency of the load-carrying structure will be demonstrated. In order to satisfy both objectives simultaneously, two initial optimisation domain models were introduced. The first was the most commonly used optimisation model with full material, while the second was a model with an initial gyroid lattice structure in the optimisation domain. The results obtained by the optimisation of the load-carrying structure were used to analyse the effect of stiffness and eigenfrequency on the four-bar mechanism path of the coupler point and the reduction of the value of the joint forces of the most loaded links. 24 refs.
Keywords: topology optimisation, shape optimisation, eigenfrequency, kinematic chain
Published in DKUM: 27.03.2025; Views: 0; Downloads: 8
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3. The MINLP approach to topology, shape and discrete sizing optimization of trussesSimon Šilih, Zdravko Kravanja, Stojan Kravanja, 2022, original scientific article Abstract: The paper presents the Mixed-Integer Non-linear Programming (MINLP) approach to the
synthesis of trusses. The solution of continuous/discrete non-convex and non-linear optimization
problems is discussed with respect to the simultaneous topology, shape and discrete sizing optimization of trusses. A truss MINLP superstructure of different topology and design alternatives
has been generated, and a special MINLP model formulation for trusses has been developed. In the
optimization model, a mass objective function of the structure has been defined and subjected to
design, load and dimensioning constraints. The MINLP problems are solved using the Modified
Outer-Approximation/Equality-Relaxation (OA/ER) algorithm. Multi-level MINLP strategies are introduced to accelerate the convergence of the algorithm. The Modified Two-Phase and the Sequential
Two-Phase MINLP strategies are proposed in order to solve highly combinatorial topology, shape
and discrete sizing optimization problems. The importance of local buckling constraints on topology
optimization is also discussed. Some simple numerical examples are shown at the end of the paper to
demonstrate the suitability and efficiency of the proposed method.
Keywords: structural synthesis, topology optimization, discrete sizing optimization, mixed-integer non-linear programming, MINLP, modified OA/ER algorithm, multi-level MINLP strategies, steel structures, trusses
Published in DKUM: 11.03.2025; Views: 0; Downloads: 3
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5. Statistics of limit root bundles relevant for exact matter spectra of F-theory MSSMsMartin Bies, Mirjam Cvetič, Mingqiang Liu, 2021, original scientific article Abstract: In the largest, currently known, class of one quadrillion globally consistent F-theory Standard Models with gauge coupling unification and no chiral exotics, the vectorlike spectra are counted by cohomologies of root bundles. In this work, we apply a previously proposed method to identify toric base threefolds, which are promising to establish F-theory Standard Models with exactly three quark doublets and no vectorlike exotics in this representation. The base spaces in question are obtained from triangulations of 708 polytopes. By studying root bundles on the quark-doublet curve Cð3;2Þ1=6 and employing well-known results about desingularizations of toric K3 surfaces, we derive a triangulation independent lower bound Nˇ ð3Þ P for the number Nð3Þ P of root bundles on Cð3;2Þ1=6 with exactly three sections. The ratio Nˇ ð3Þ P =NP, where NP is the total number of roots on Cð3;2Þ1=6 , is largest for base spaces associated with triangulations of the eighth three-dimensional polytope Δ∘ 8 in the Kreuzer-Skarke list. For each of these Oð1015Þ threefolds, we expect that many root bundles on Cð3;2Þ1=6 are induced from F-theory gauge potentials and that at least every 3000th root on Cð3;2Þ1=6 has exactly three global sections and thus no exotic vectorlike quark-doublet modes.
Keywords: astrophysics, compactification, string theory models, geometry, higher-dimensional field theories, mathematical physics, quantum fields in curved spacetime, string phenomenology, supersymmetric models, topology
Published in DKUM: 16.10.2023; Views: 317; Downloads: 33
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6. Reflections on the matter of 3D N=1 vacua and local Spin(7) compactificationsMirjam Cvetič, Jonathan J. Heckman, Ethan Torres, Gianluca Zoccarato, 2022, original scientific article Abstract: We use Higgs bundles to study the 3D N = 1 vacua obtained from M-theory compactified on a local Spin(7) space given as a four-manifold M-4 of ADE singularities with further generic enhancements in the singularity type along one-dimensional subspaces. There can be strong quantum corrections to the massless degrees of freedom in the low energy effective field theory, but topologically robust quantities such as "parity" anomalies are still calculable. We show how geometric reflections of the compactification space descend to 3D reflections and discrete symmetries. The parity anomalies of the effective field theory descend from topological data of the compactification. The geometric perspective also allows us to track various perturbative and nonperturbative corrections to the 3D effective field theory. We also provide some explicit constructions of well-known 3D theories, including those which arise as edge modes of 4D topological insulators, and 3D N = 1 analogs of grand unified theories. An additional result of our analysis is that we are able to track the spectrum of extended objects and their transformations under higher-form symmetries.
Keywords: Compactification, geometry, M-theory, quantum field theory, string theory techniques in condensed matter, strings & branes, supersymmetry, topology
Published in DKUM: 25.09.2023; Views: 305; Downloads: 30
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7. Interoperability of infrastructure and transportation information models: A public transport case studyNenad Čuš Babič, Sara Guerra de Oliveira, Andrej Tibaut, 2022, original scientific article Abstract: The duplication of semantic data modelled in different disciplines poses interoperability challenges. Information models that benefit from the application of standards that enable data reusability and prevent redundancy and misuse should be compatible, particularly when different systems are used in the same domain-specific area, as in the case of public transportation. Transportation information models, leading and providing reliable and robust public transport services, can nowadays be enriched with information found in building information models devoted to transportation infrastructure. Therefore, in the present paper, a mapping between the standards and technical specifications that support each modelling approach is explored, analysed, and aligned to maximise the best out of the current common practices used. The information from the Industry Foundation Classes IFC specification-based models complements the conceptual and physical transportation models, where Transmodel and NeTEx are well-established, with accurate (as-built) detailed characteristics of the transportation infrastructure (stop places, quays, entrances, access spaces and equipment as ramps, staircases, and escalators). The extraction of topological information stored in IFC models allows for navigation-network extraction, information about spaces, and passages between spaces. A specific public transport case study focused on a train station is detailed to better corroborate and illustrate the advantages and uses of compatible and complementing modelling approaches. As building-information-modelling awareness and use is growing, the validated mapping approach can benefit from the future application of automation procedures.
Keywords: transmodel, NeTEx, IFC, interoperability, building topology, navigation network
Published in DKUM: 22.09.2023; Views: 540; Downloads: 397
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8. Designing the gear body structure to control vibration behaviourRiad Ramadani, 2018, doctoral dissertation Abstract: This research presents a new approach aiming to reduce gear vibration as well as its weight by modifying the gear body structure. The primary objective was to reduce vibration and noise emission of spur gears. For this purpose, a solid gear body was replaced by a cellular lattice structure, which was expected to raise the torsional elasticity of the gear body. The cellular lattice structure was designed and optimized by FE-based topology optimization software CAESS ProTOp, which is based on strain energy control. For experimental purposes, the optimized gear was produced from Titanium alloy Ti-6Al-4V ELI by using Selective Laser Melting technique. A polymer matrix was added to increase the damping of the structure.
In order to test the gears, a new test rig with closed loop was conceived, designed and produced. The test rig is equipped with two gear pairs: with the tested one and with the driving one. The gears have been run and tested at different speeds and torque. The acceleration, strain and sound pressure of a running gear pair was measured. The final processing of the signal was done by a specially developed software based on LabView. By employing the fast Fourier transformation the time signal of acceleration, strain and sound pressure has been converted to the frequency spectrum and time frequency spectrogram. The results obtained by testing the solid and cellular lattice gear body were compared. It was experimentally confirmed that the cellular lattice structure of a gear body and addition of a polymer matrix may significantly reduce the vibration.
Keywords: Gear vibration, cellular lattice structure, topology optimization, test rig
Published in DKUM: 27.02.2018; Views: 2496; Downloads: 269
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9. Effective topological charge cancelation mechanismLuka Mesarec, Wojciech Góźdź, Aleš Iglič, Samo Kralj, 2016, original scientific article Abstract: Topological defects (TDs) appear almost unavoidably in continuous symmetry breaking phase transitions. The topological origin makes their key features independent of systems’ microscopic details; therefore TDs display many universalities. Because of their strong impact on numerous material properties and their significant role in several technological applications it is of strong interest to find simple and robust mechanisms controlling the positioning and local number of TDs. We present a numerical study of TDs within effectively two dimensional closed soft films exhibiting in-plane orientational ordering. Popular examples of such class of systems are liquid crystalline shells and various biological membranes. We introduce the Effective Topological Charge Cancellation mechanism controlling localised positional assembling tendency of TDs and the formation of pairs {defect, antidefect} on curved surfaces and/or presence of relevant “impurities” (e.g. nanoparticles). For this purpose, we define an effective topological charge Δmeff consisting of real, virtual and smeared curvature topological charges within a surface patch Δς identified by the typical spatially averaged local Gaussian curvature K. We demonstrate a strong tendency enforcing Δmeff → 0 on surfaces composed of Δς exhibiting significantly different values of spatially averaged K. For Δmeff ≠ 0 we estimate a critical depinning threshold to form pairs {defect, antidefect} using the electrostatic analogy.
Keywords: topological defects, topological charge, numerical studies, orientational ordering, nematic liquid crystals, liquid crystalline shells, biological membranes, nanoparticles, Gaussian curvature, electrostatic analogy, annihilation, topology
Published in DKUM: 23.06.2017; Views: 1141; Downloads: 351
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10. Inverse limits in the category of compact Hausdorff spaces and upper semicontinuous functionsIztok Banič, Tina Sovič, 2013, original scientific article Abstract: V članku obravnavamo inverzne limite v kategoriji ▫$mathcal{CHU}$▫ kompaktnih Hausdorffovih prostorov in navzgor polzveznih (u.s.c) preslikav. Vpeljemo pojem šibkih inverznih limit in pokažemo, da inverzne limite z navzgor polzveznimi veznimi preslikavami skupaj s projekcijami niso nujno inverzne limite v ▫$mathcal{CHU}$▫, so pa vedno šibke inverzne limite v tej kategoriji. Med drugim gre za realizacijo kategorijalnega pristopa k reševanju problema, ki ga je zastavil W. T. Ingram.
Keywords: topologija, kategorije, navzgor polzvezne funkcije, inverzne limite, posplošene inverzne limite, šibke inverzne limite, topology, upper semi-continuous functions, inverse limits, generalized inverse limits, weak inverse limits
Published in DKUM: 10.07.2015; Views: 27193; Downloads: 100
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