481. The genus Fomitopsis (Polyporales, Basidiomycota) reconsideredViacheslav Spirin, K. Runnel, J. Vlasák, I. Viner, M.D. Barrett, L. Ryvarden, Annarosa Bernicchia, B. Rivoire, A.M. Ainsworth, Tine Grebenc, 2024, izvirni znanstveni članek Povzetek: Based on seven- and three-gene datasets, we discuss four alternative approaches for a reclassification of Fomitopsidaceae (Polyporales, Basidiomycota). After taking into account morphological diversity in the family, we argue in favour of distinguishing three genera only, viz. Anthoporia, Antrodia and Fomitopsis. Fomitopsis becomes a large genus with 128 accepted species, containing almost all former Fomitopsis spp. and most species formerly placed in Antrodia, Daedalea and Laccocephalum. Genera Buglossoporus, Cartilosoma, Daedalea, Melanoporia, Neolentiporus, alongside twenty others, are treated as synonyms of Fomitopsis. This generic scheme allows for morphologically distinct genera in Fomitopsidaceae, unlike other schemes we considered. We provide arguments for retaining Fomitopsis and suppressing earlier (Daedalea, Caloporus) or simultaneously published generic names (Piptoporus) considered here as its synonyms. Taxonomy of nine species complexes in the genus is revised based on ITS, ITS + TEF1, ITS + TEF1 + RPB1 and ITS + TEF1 + RPB2 datasets. In total, 17 species are described as new to science, 26 older species are reinstated and 26 currently accepted species names are relegated to synonymy. A condensed identification key for all accepted species in the genus is provided.
Ključne besede: brown-rot fungi, new taxa, phylogeny, polypores, taxonomy
Objavljeno v DiRROS: 28.02.2024; Ogledov: 127; Prenosov: 64
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482. Effect of heat treatment on thermal conductivity of additively manufactured AISI H13 tool steelSamo Tome, Blaž Karpe, Irena Paulin, Matjaž Godec, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: AISI H13 is commonly used for tooling, where higher wear resistance, thermal fatigue resistance, or hot toughness is required. Such examples include forging dies, plastic molds, hot shear blades, high-pressure die casting, and extrusion dies. Thus, thermal conductivity is one of the most important factors for hot work tools. Typically, the work cycle of a hot work tool designed for forging consists of four main phases: the forging stroke, with which the die imparts its shape onto the part, a brief pause while the die is reset to its original position, a lubrication phase, and a post lubrication dwell phase. During the forging phase, a significant amount of heat is transferred to the die while it is in contact with the part. This heat must then be dispelled for the part to return to a working temperature. While somewhat different, other hot work processes mentioned above are similar in that the hot work tool gets heated to a high temperature due to the contact with the object of deformation. The process of additive manufacturing (AM) promises better, more efficient tool production with features like conforming cooling channels, which would reduce the thermal fatigue of tools, prolonging tool life. However, the powder bed fusion (PBF) method creates a columnar microstructure, which has a detrimental effect on the thermal conductivity of H13 tool steel. Our investigation focused on the beneficial effect of heat treatment, specifically annealing at different temperatures, on the thermal conductivity of AM-produced H13 parts.
Ključne besede: SLM, thermal conductivity, tool steel, heat treatment
Objavljeno v DiRROS: 28.02.2024; Ogledov: 113; Prenosov: 65
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483. Extreme environments simplify reassembly of communities of arbuscular mycorrhizal fungiNataša Šibanc, Dave R. Clark, Thorunn Helgason, Alex J. Dumbrell, Irena Maček, 2024, izvirni znanstveni članek Povzetek: The ecological impacts of long-term (press) disturbance on mechanisms regulating the relative abundance (i.e., commonness or rarity) and temporal dynamics of species within a community remain largely unknown. This is particularly true for the functionally important arbuscular mycorrhizal (AM) fungi; obligate plant-root endosymbionts that colonize more than two-thirds of terrestrial plant species. Here, we use high-resolution amplicon sequencing to examine how AM fungal communities in a specific extreme ecosystem—mofettes or natural CO2 springs caused by geological CO2 exhalations—are affected by long-term stress. We found that in mofettes, specific and temporally stable communities form as a subset of the local metacommunity. These communities are less diverse and dominated by adapted, “stress tolerant” taxa. Those taxa are rare in control locations and more benign environments worldwide, but show a stable temporal pattern in the extreme sites, consistently dominating the communities in grassland mofettes. This pattern of lower diversity and high dominance of specific taxa has been confirmed as relatively stable over several sampling years and is independently observed across multiple geographic locations (mofettes in different countries). This study implies that the response of soil microbial community composition to long-term stress is relatively predictable, which can also reflect the community response to other anthropogenic stressors (e.g., heavy metal pollution or land use change). Moreover, as AM fungi are functionally differentiated, with different taxa providing different benefits to host plants, changes in community structure in response to long-term environmental change have the potential to impact terrestrial plant communities and their productivity
Ključne besede: arbuscular mycorrhiza, elevated CO2, long-term experiments, soil biodiversity, soil hypoxia, next-generation sequencing, NGS
Objavljeno v DiRROS: 28.02.2024; Ogledov: 131; Prenosov: 63
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484. Development of the recycling procedure for rapid antigen testsRebeka Rudolf, Darja Feizpour, Žiga Jelen, Peter Majerič, Tilen Švarc, Matej Zadravec, Timi Gomboc, Aleksandra Kocijan, 2024, izvirni znanstveni članek Ključne besede: rapid antigen tests, recycling, characterization, nanogold, plastic
Objavljeno v DiRROS: 28.02.2024; Ogledov: 142; Prenosov: 58
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485. A numerical study of gas focused non-Newtonian micro-jetsRizwan Zahoor, Saša Bajt, Božidar Šarler, 2024, izvirni znanstveni članek Ključne besede: serial crystallography, micro jets, multiphase flow, fluid rheology, non-Newtonian fluid, flow focusing
Objavljeno v DiRROS: 28.02.2024; Ogledov: 117; Prenosov: 58
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486. A hybrid radial basis function-finite difference method for modelling two-dimensional thermo-elasto-plasticity : Application to cooling of hot-rolled steel bars on a cooling bedGašper Vuga, Boštjan Mavrič, Umut Hanoglu, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: This paper represents Part 2 of the parallel paper Part 1, where the strong form hybrid RBF-FD method was developed for solving thermo-elasto-plastic problems. It addresses the industrial application of this novel meshless method to steel bars cooling on a cooling bed (CB) where the formation of residual stress is of primary interest. The study investigates the impact of the distance between the bars and the distance to the heat shield above the CB on radiative heat fluxes and, consequently, on thermo-mechanical response. The thermal model is solved on bars cross-section with a RBF-FD method where augmented polyharmonic splines are used for the local approximation. View factors, computed with a Monte-Carlo method, are included in radiative heat fluxes. The thermal solution is incrementally applied on a mechanical model that assumes a generalised plane strain state and captures bars bending. The study employs a hybrid RBF-FD method to resolve a nonlinear discontinuous mechanical problem successfully. The simulation of the process shows how different process parameters influence the thermo-mechanical response of the bars.
Ključne besede: steel bars, cooling bed, thermo-mechanical modelling, hybrid radial basis function, generated finite differences, residual stresses
Objavljeno v DiRROS: 28.02.2024; Ogledov: 104; Prenosov: 63
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487. A hybrid radial basis function-finite difference method for modelling two-dimensional thermo-elasto-plasticity, Part 1 : method formulation and testingGašper Vuga, Boštjan Mavrič, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: A hybrid version of the strong form meshless Radial Basis Function-Finite Difference (RBF-FD) method is introduced for solving thermo-mechanics. The thermal model is spatially discretised with RBF-FD, where trial functions are polyharmonic splines augmented with polynomials. For time discretisation, the explicit Euler method is employed. An extension of RBF-FD, the hybrid RBF-FD, is introduced for solving mechanical problems. The model is one-way coupled, where temperature affects displacements. The thermo-elastoplastic material response is considered where the stress field is generally non-smooth. The hybrid RBF-FD, where the finite difference method is used to discretise the divergence operator from the balance equation, is shown to be successful when dealing with such problems. The mechanical model is introduced in a plane strain and in a generalised plane strain (GPS) assumption. For the first time, this work presents a strong form RBF-FD for GPS problems subjected to integral form constraints. The proposed method is assessed regarding h-convergence and accuracy on the benchmark with heating an elastoplastic square. It is proven to be successful at solving one-way coupled thermo-elastoplastic problems. The proposed novel meshless approach is efficient, accurate, and robust. Its use in an industrial situation is provided in Part 2 of this paper.
Ključne besede: thermo-mechanical modelling, von Mises small strain plasticity, hybrid radial basis function generated finite differences, polyharmonic splines
Objavljeno v DiRROS: 28.02.2024; Ogledov: 107; Prenosov: 59
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488. Formulation of the method of fundamental solutions for two-phase Stokes flowZlatko Rek, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: The method of fundamental solutions with a subdomain technique is used for the solution of the free boundary problem associated with a two-phase Stokes flow in a 2D geometry. The solution procedure is based on the collocation of the boundary conditions with the Stokeslets. It is formulated for the flow of unmixing fluids in contact, where the velocity, pressure field, and position of the free boundary between the fluids must be determined. The standard formulation of the method of fundamental solutions is, for the first time, upgraded for the case with mixed velocity and pressure boundary conditions and verified on a T-splitter single-phase flow with unsymmetric pressure boundary conditions. The standard control volume method is used for the reference solution. The accurate evaluation of the velocity derivatives, which are required to calculate the balance of forces at the free boundary between the fluids, is achieved in a closed form in contrast to previous numerical attempts. An algorithm for iteratively calculating the position of the free boundary that involves displacement, smoothing and repositioning of the nodes is elaborated. The procedure is verified for a concurrent flow of two fluids in a channel. The velocity and velocity derivatives show fast convergence to the analytical solution. The developed boundary meshless method is easy to code, accurate and computationally efficient since only collocation at the fixed and free boundaries is needed.
Ključne besede: Stokes equations, two-phase flow, free boundary problems, method of fundamental solutions, subdomain technique
Objavljeno v DiRROS: 28.02.2024; Ogledov: 103; Prenosov: 58
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489. General position polynomialsVesna Iršič, Sandi Klavžar, Gregor Rus, James Tuite, 2024, izvirni znanstveni članek Povzetek: A subset of vertices of a graph $G$ is a general position set if no triple of vertices from the set lie on a common shortest path in $G$. In this paper we introduce the general position polynomial as $\sum_{i \geq 0} a_i x^i$, where $a_i$ is the number of distinct general position sets of $G$ with cardinality $i$. The polynomial is considered for several well-known classes of graphs and graph operations. It is shown that the polynomial is not unimodal in general, not even on trees. On the other hand, several classes of graphs, including Kneser graphs $K(n,2)$, with unimodal general position polynomials are presented.
Ključne besede: general position set, general position number, general position polynomial, unimodality, trees, Cartesian product of graphs, Kneser graphs
Objavljeno v DiRROS: 28.02.2024; Ogledov: 106; Prenosov: 75
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490. An improved local radial basis function method for solving small-strain elasto-plasticityGašper Vuga, Boštjan Mavrič, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: Strong-form meshless methods received much attention in recent years and are being extensively researched and applied to a wide range of problems in science and engineering. However, the solution of elasto-plastic problems has proven to be elusive because of often non-smooth constitutive relations between stress and strain. The novelty in tackling them is the introduction of virtual finite difference stencils to formulate a hybrid radial basis function generated finite difference (RBF-FD) method, which is used to solve small-strain von Mises elasto-plasticity for the first time by this original approach. The paper further contrasts the new method to two alternative legacy RBF-FD approaches, which fail when applied to this class of problems. The three approaches differ in the discretization of the divergence operator found in the balance equation that acts on the non-smooth stress field. Additionally, an innovative stabilization technique is employed to stabilize boundary conditions and is shown to be essential for any of the approaches to converge successfully. Approaches are assessed on elastic and elasto-plastic benchmarks where admissible ranges of newly introduced free parameters are studied regarding stability, accuracy, and convergence rate.
Ključne besede: Von Mises elasto-plasticity, radial basis function, finite differences, polyharmonic splines, two dimensions, hybrid discretization
Objavljeno v DiRROS: 28.02.2024; Ogledov: 105; Prenosov: 56
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