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2. SOLVING CONCRETE PROBLEMS IN NAVAL FRAMEWORK THROUGH CANONICAL MATHEMATICAL MODELSIrina Cristea, Camelia Ciobanu, Claudia Pantelie, 2015, izvirni znanstveni članek Opis: The paper aims is to point out how good results in the management of shipping might be achieved through canonical mathematical models. Najdeno v: ključnih besedah Povzetek najdenega: ...mathematical model, North-west corner method, minimum element method, mixed differences method.... Ključne besede: mathematical model, North-west corner method, minimum element method, mixed differences method. Objavljeno: 09.02.2016; Ogledov: 2766; Prenosov: 3 Polno besedilo (212,38 KB) |
3. Development and characterization of improved materials for antifouling applicationsUrška Lavrenčič Štangar, Iztok Arčon, Tihana Čižmar, 2015, objavljeni povzetek znanstvenega prispevka na konferenci Najdeno v: ključnih besedah Povzetek najdenega: ...sol-gel method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic... Ključne besede: sol-gel method, photocatalysis, hybrid materials, Cu K-edge XANES, photocatalytic activity Objavljeno: 15.02.2016; Ogledov: 3143; Prenosov: 0 Polno besedilo (131,22 KB) |
4. INNOVATIVE METHODS FOR IMAGING WITH THE USE OF X-RAY FREE ELECTRON LASER (XFEL) AND SYNCHROTRON SOURCESBoštjan Mavrič, Grega Belšak, Marjan Maček, N. Talat, Rizwan Zahoor, Božidar Šarler, 2016, projektna dokumentacija (idejni projekt, izvedbeni projekt) Najdeno v: ključnih besedah Povzetek najdenega: ...XFEL, simulation, microjet, gas, method of fundamental solutions... Ključne besede: XFEL, simulation, microjet, gas, method of fundamental solutions Objavljeno: 20.06.2016; Ogledov: 4034; Prenosov: 0 Polno besedilo (66,05 KB) |
5. Non-Singular Method of Fundamental Solutions for Two-dimensional ThermoelasticityBožidar Šarle, liu qingguo, objavljeni povzetek znanstvenega prispevka na konferenci Opis: A framework for simulation of thermomechanical processing of microstructures by the method of fundamental solutions, free of artificial boundary, is shown. The formulation of the method for two-dimensional thermal and mechanical models is presented. In particular, the formulation for thermo-elastic problems is discussed. In the thermal and mechanical models, the concentrated point sources are replaced by the distributed sources over the sphere around the singularity to regularize the singularities and the balance of forces is used to calculate some of the otherwise singular diagonal coefficients. This procedure enables also for solving problems with internal voids and inclusions. The novel boundary meshless method has been assessed by comparison with MFS and analytical solution. The method is easy to code, accurate, and efficient. Najdeno v: ključnih besedah Ključne besede: thermomechanics, elasticity, plasticity, non-singular method of fundamental solutions, three-dimensions, microstructures Objavljeno: 28.06.2016; Ogledov: 2983; Prenosov: 0 Polno besedilo (239,40 KB) |
6. Method of Regularized Sources for Stokes Flow Problems with Improved Calculation of Velocity Derivatives at the Boundarywen shiting, Božidar Šarler, li ming, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The solution of Stokes flow problems with Dirichlet and Neumann boundary conditions is performed by a non-singular Method of Fundamental Solutions which does not require artificial boundary, i.e. source points of fundamental solution coincide with the collocation points on the boundary. Instead of Dirac delta force, an exponential function, called blob, with a free parameter epsilon is employed, which limits to Dirac delta function when epsilon limits to zero. The solution of the problem is sought as a linear combination of the fields due to the regularized sources that coincide with the boundary and with their intensities chosen in such a way that the solution complies with the boundary conditions. A two-dimensional flow between parallel plates is chosen to assess the properties of the method. The results of the method are accurate except for the derivatives at the boundary. A correction of the method is proposed which can be used to properly assess also the derivatives at the boundary Najdeno v: ključnih besedah Ključne besede: stokes flow, method of regularized sources, meshless method Objavljeno: 28.06.2016; Ogledov: 2633; Prenosov: 0 Polno besedilo (247,45 KB) |
7. A non-singular method of fundamental solutions for two-dimensional steady-state isotropic thermoelasticity problemsqingguo liu, Božidar Šarler, 2017, izvirni znanstveni članek Opis: We consider a boundary meshless numerical solution for two-dimensional linear static thermoelastic problems. The formulation of the problem is based on the approach of Marin and Karageorghis, where the Laplace equation for the temperature ﬁeld is solved ﬁrst, followed by a particular solution of the non-homogenous term in the Navier-Lamé system for the displacement, the solution of the homogenous equilibrium equations, and ﬁnally the application of the superposition principle. The solution of the problem is based on the method of fundamental solutions (MFS) with source points on the boundary. This is, by complying with the Dirichlet boundary conditions, achieved by the replacement of the concentrated point sources with distributed sources over the disk around the singularity, and for complying with the Neumann boundary conditions by assuming a balance of the heat ﬂuxes and the forces. The derived non-singular MFS is assessed by a comparison with analytical solutions and the MFS for problems that can include diﬀerent materials in thermal and mechanical contact. The method is easy to code, accurate, eﬃcient and represents a pioneering attempt to solve thermoelastic problems with a MFS-type method without an artiﬁcial boundary. The procedure makes it possible to solve a broad spectra of thermomechanical problems. Najdeno v: ključnih besedah Ključne besede: Keywords: Isotropic thermoelasticity Meshless method Non-singular method of fundamental solutions Collocation Eﬃcient desingularisation Objavljeno: 23.12.2016; Ogledov: 2738; Prenosov: 0 Polno besedilo (2,54 MB) |
8. Growth of nanostructured ZnO on wearable fabrics for functional garmentMinseo ParK, Fei Tong, Achintya Sujan, Yoonsung Chung, Minseo Park, Bruce Tatarchuk, Helen Koo, Hosang Ahn, Young Soo Yoon, Dong-Joo Kim, 2014, izvirni znanstveni članek Najdeno v: ključnih besedah Povzetek najdenega: ...ZnO, Fabrics, Dip-pad-cure method, Nanorods, Diffuse reflectance, IV measurement... Ključne besede: ZnO, Fabrics, Dip-pad-cure method, Nanorods, Diffuse reflectance, IV measurement Objavljeno: 16.01.2017; Ogledov: 2546; Prenosov: 0 Polno besedilo (918,15 KB) |
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10. Meshless modeling of thermo-mechanics of low-frequency electromagnetic direct chill castingBoštjan Mavrič, 2017, doktorska disertacija Opis: The aim of this dissertation is to devise a meshless model describing the thermomechanical phenomena, which occur during DC casting of aluminium alloys under the influence of electromagnetic stirring. The thermoemchanical phenomena are important, because they can cause several type of defects, which can significantly deteriorate the quality of the resulting billet. The two most important of them are the hot tearing, which causes cracks to appear in the mushy zone, and the porosity, which demonstrates itself as micrometer sized voids in the microstructure of the billet.
To calculate the stresses and strains, a computational model of the stationary state of the process, stated in axial symmetry, is formulated. It uses Eulerian formulation by fixing the computational domain to the mold of the casting device allowing the material to move through the computational domain. The stresses are calculated from the stress equilibrium equations. The small strain approximation is used to consider the three contributions to strain. The strain consists of the thermal strain, which is caused by the inhomogeneous thermal profile in the billet, the viscoplastic strain, which is caused by the irreversible deformation because of the large stresses occurring in the billet, and the elastic strain.
The spatial discretization of the governing equations is performed by local radial basis function collocation method (LRBFCM) and the temporal discretization is achieved by the method of lines with implicit Euler formula. The method used for spatial discretization uses radial basis functions augmented by monomials to approximate the solution values on localized stencils. This approximation is used to construct the discretization coefficients of the differential operators present in the model. A flexible framework for formulation of multiphysics problems is developed to use the obtained discretization coefficients to construct the temporal discretization of the governing equations. The node arrangement, on which the spatial discretization is performed, was generated by a point-repel algorithm.
The performance of the method is tested on several benchmark test cases. The accuracy of the discretization is estimated by comparing the analytic and the numerical solution to several stationary problems in thermomechancis. Of special interest is the performance of the method with respect to the choice of the shape parameter, which determines the spatial scale of the radial basis functions. Besides this, the dependence of the condition number of the interpolation matrix on the shape parameter is studied. The condition number is found fit to replace the condition number as the shape-determining free parameter of the method.
The implementation of the solver of time dependent problems is tested on problem of thermoelasticity, which couples the thermal transport with the elastic waves. The results of the problem are compared with the finite element method, showing good agreement of the two methods. The results are also compared with the results obtained by meshless local Petrov-Galerkin method and the proposed local collocation method demonstrated significantly better solution quality in the studied case.
The performance of the solver used to solve the system of nonlinear equations given by the viscoplastic constitutive equations is estimated on a quasi zero-dimensional problem. The results are found to match perfectly. Solution of a more complicated problem is obtained with the proposed method and the finite-element method, both methods giving practically the same solution, although some serious limitations of the chosen finite element solver are exposed during the selection of the problem parameters.
Finally, the devised method is applied to the problem of DC casting of aluminium alloys. The thermomechanical model relies on a model of heat and mass transfer to obtain the input fields needed in the solver. The required fields are: temperature, pressure, liquid Najdeno v: ključnih besedah Povzetek najdenega: ...performed by local radial basis function collocation method (LRBFCM) and the temporal discretization is achieved... Ključne besede: thermomechanics, viscoplasticity, aluminium alloys, direct-chill casting, electromagnetic stirring, hot tearing, porosity, meshless methods, local collocation method, radial basis functions, shape parameter Objavljeno: 28.06.2017; Ogledov: 3289; Prenosov: 118 Polno besedilo (21,30 MB) |