1. A family of $C^1$ Clough-Tocher spline spaces on $C^0$ piecewise quadratic domain partitionsJan Grošelj, Marjetka Knez, 2025, izvirni znanstveni članek Povzetek: The paper addresses the construction of $C^1$ splines on a curved domain that is parametrized by a $C^0$ piecewise geometry mapping composed of quadratic Bézier triangles. The $C^1$ splines are assembled from polynomials of a chosen total degree greater than or equal to four, and their construction is based on the Clough-Tocher splitting technique that ensures locality. In particular, the splines are locally characterized by an interpolation problem described by Hermite data, which resembles the standard macro-element concepts developed for $C^1$ splines on triangulations.
Ključne besede: quadratic triangle, quadratic triangulation, isogeometric functions, Clough-Tocher refinement, spline space, dimension, basis functions
Objavljeno v DiRROS: 24.03.2025; Ogledov: 506; Prenosov: 281
 Celotno besedilo (5,58 MB)
Gradivo ima več datotek! Več... |
2. Simulation of temperature field in steel billets during reheating in pusher-type furnace by meshless methodQingguo Liu, Umut Hanoglu, Zlatko Rek, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: Using a meshless method, a simulation of steel billets in a pusher-type reheating furnace is carried out for the first time. The simulation represents an affordable way to replace the measurements. The heat transfer from the billets with convection and radiation is considered. Inside each of the billets, the heat diffusion equation is solved on a two-dimensional central slice of the billet. The diffusion equation is solved in a strong form by the Local Radial Basis Function Collocation Method (LRBFCM) with explicit time-stepping. The ray tracing procedure solves the radiation, where the view factors are computed with the Monte Carlo method. The changing number of billets in the furnace at the start and the end of the loading and unloading of the furnace is considered. A sensitivity study on billets' temperature evolution is performed as a function of a different number of rays used in the Monte Carlo method, different stopping times of the billets in the furnace, and different spacing between the billets. The temperature field simulation is also essential for automatically optimizing the furnace’s productivity, energy consumption, and the billet’s quality. For the first time, the LRBFCM is successfully demonstrated for solving such a complex industrial problem.
Ključne besede: pusher-type reheating furnace, steel, temperature field, radiation, convection, diffusion, strong form meshless method, radial basis functions
Objavljeno v DiRROS: 20.12.2024; Ogledov: 688; Prenosov: 395
Celotno besedilo (4,35 MB)
Gradivo ima več datotek! Več... |
3. |
4. |
5. Domains without parabolic minimal submanifolds and weakly hyperbolic domainsFranc Forstnerič, 2023, izvirni znanstveni članek Povzetek: We show that if $\Omega$ is an $m$-convex domain in $\mathbb{R}^n$ for some $2 \le m < n$ whose boundary $b\Omega$ has a tubular neighbourhood of positive radius and is not $m$-flat near infinity, then $\Omega$ does not contain any immersed parabolic minimal submanifolds of dimension $\ge m$. In particular, if $M$ is a properly embedded non-flat minimal hypersurface in $\mathbb{R}^n$ with a tubular neighbourhood of positive radius, then every immersed parabolic hypersurface in $\mathbb{R}^n$ intersects $M$. In dimension $n=3$, this holds if $M$ has bounded Gaussian curvature function. We also introduce the class of weakly hyperbolic domains $\Omega$ in $\mathbb{R}^n$, characterised by the property that every conformal harmonic map $\mathbb{C} \to \Omega$ is constant, and we elucidate their relationship with hyperbolic domains, and domains without parabolic minimal surfaces.
Ključne besede: minimal surfaces, m-plurisubharmonic functions, hyperbolic domain
Objavljeno v DiRROS: 10.04.2024; Ogledov: 1415; Prenosov: 914
Celotno besedilo (242,50 KB)
Gradivo ima več datotek! Več... |
6. On a definition of logarithm of quaternionic functionsGraziano Gentili, Jasna Prezelj, Fabio Vlacci, 2023, izvirni znanstveni članek Povzetek: For a slice-regular quaternionic function $f$, the classical exponential function ${\mathrm exp} f$ is not slice-regular in general. An alternative definition of an exponential function, the $\ast$-exponential ${\mathrm exp}_\ast$, was given in the work by Altavilla and de Fabritiis (2019): if $f$ is a slice-regular function, then ${\mathrm exp}_\ast f$ is a slice-regular function as well. The study of a $\ast$-logarithm ${\mathrm log}_\ast f$ of a slice-regular function $f$ becomes of great interest for basic reasons, and is performed in this paper. The main result shows that the existence of such a ${\mathrm log}_\ast f$ depends only on the structure of the zero set of the vectorial part $f_v$ of the slice-regular function $f = f_0 + f_v$, besides the topology of its domain of definition. We also show that, locally, every slice-regular nonvanishing function has a $\ast$-logarithm and, at the end, we present an example of a nonvanishing slice-regular function on a ball which does not admit a $\ast$-logarithm on that ball.
Ključne besede: regular functions over quaternions, quaternionic logarithm of slice-regular functions
Objavljeno v DiRROS: 10.04.2024; Ogledov: 1000; Prenosov: 545
Celotno besedilo (425,44 KB)
Gradivo ima več datotek! Več... |
7. Generalized Pell graphsVesna Iršič Chenoweth, Sandi Klavžar, Elif Tan, 2023, izvirni znanstveni članek Povzetek: In this paper, generalized Pell graphs $\Pi_{n,k}$, $k\ge 2$, are introduced. The special case of $k=2$ are the Pell graphs $\Pi_{n}$ defined earlier by Munarini. Several metric, enumerative, and structural properties of these graphs are established. The generating function of the number of edges of $\Pi_{n,k}$ and the generating function of its cube polynomial are determined. The center of $\Pi_{n,k}$ is explicitly described; if $k$ is even, then it induces the Fibonacci cube $\Gamma_{n}$. It is also shown that $\Pi_{n,k}$ is a median graph, and that $\Pi_{n,k}$ embeds into a Fibonacci cube.
Ključne besede: Fibonacci cubes, Pell graphs, generating functions, center of graph, median graphs, k-Fibonacci sequence
Objavljeno v DiRROS: 08.04.2024; Ogledov: 992; Prenosov: 544
Celotno besedilo (345,71 KB)
Gradivo ima več datotek! Več... |
8. Effects of chronic physical exercise on executive functions and episodic memory in clinical and healthy older adult populations : a systematic review and meta-analysis protocolSoledad Ballesteros, Andreea Badache, Vera Belkin, Christoforos D. Giannaki, Antonia Kaltsatou, Uroš Marušič, Mohammad Mosaferi Ziaaldini, Manca Peskar, José M. Reales, Jennifer A. Rieker, 2024, pregledni znanstveni članek Povzetek: Background Executive functions (EFs) and episodic memory are fundamental components of cognition that deteriorate with age and are crucial for independent living. While numerous reviews have explored the effect of exercise on these components in old age, these reviews screened and analyzed selected older adult populations, or specific exercise modes, thus providing only limited answers to the fundamental question on the effect of exercise on cognition in old age. This article describes the protocol for a systematic review and multilevel meta-analytic study aiming at evaluating the effectiveness of different types of chronic exercise in improving and/or maintaining EFs and long-term episodic memory in older adults. Methods and analysis The study protocol was written in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Several databases will be searched. Randomized controlled trials (RCTs) conducted in older adults aged ≥ 60 years providing any kind of planned, structured, and repetitive exercise interventions, and EFs and/or episodic memory measures as outcomes, published in English in peer-reviewed journals and doctoral dissertations will be included. Two independent reviewers will screen the selected articles, while a third reviewer will resolve possible conflicts. The Cochrane risk-of-bias tool will be used to assess the quality of the studies. Finally, data will be extracted from the selected articles, and the formal method of combining individual data from the selected studies will be applied using a random effect multilevel meta-analysis. The data analysis will be conducted with the metafor package in R. Discussion and conclusion This review will synthesize the existing evidence and pinpoint gaps existing in the literature on the effects of exercise on EFs and episodic memory in healthy and unhealthy older adults. Findings from this meta-analysis will help to design effective exercise interventions for older adults to improve and/or maintain EFs and episodic memory. Its results will be useful for many researchers and professionals working with older adults and their families.
Ključne besede: diseased older adults, healthy older adultsi, episodic memory, executive functions, exercises, three level meta analysis, tri-nivojska meta-analiza
Objavljeno v DiRROS: 03.04.2024; Ogledov: 1308; Prenosov: 586
Celotno besedilo (1,18 MB)
Gradivo ima več datotek! Več... |
9. |
10. Effects of COVID-19 on cognition and mood after hospitalization and at 2-month follow-upManca Peskar, Boštjan Šimunič, Luka Šlosar, Saša Pišot, Kaja Teraž, Mladen Gasparini, Rado Pišot, Uroš Marušič, 2023, izvirni znanstveni članek Povzetek: A plethora of evidence links SARS-CoV-2 infection with concomitant cognitive dysfunction, which often persists weeks to months after the acute stages of illness and affects executive function, attention, memory, orientation, and movement control. It remains largely unclear which conditions or factors exacerbate the recovery. In a cohort of N=37 Slovenian patients (5 females, aged M = 58, SD = 10.7 years) that were hospitalized because of COVID-19, the cognitive function and mood states were assessed immediately after discharge and 2-months later to investigate the early post-COVID recovery changes. We assessed the global Montreal Cognitive Assessment (MoCA), Simple and Choice Reaction Times, executive functions (Trail-Making Test – TMT-A and TMT-B), short-term memory (Auditory Verbal Learning Test – AVLT), and visuospatial memory. We monitored depressive and anxiety symptoms and applied general self-efficacy and cognitive complaints questionnaires. Our results showed a global cognitive impairment (MoCA, Z = 332.5; p = 0.012), poorer performance on executive functions (TMT-A, Z = 188; p = 0.014; and TMT-B, Z = 185; p = 0.012), verbal memory (AVLT, F = 33.4; p < 0.001), and delayed recall (AVLT7, F = 17.1; p < 0.001), and higher depressive (Z = 145; p = 0.015) and anxiety (Z = 141; p = 0.003) symptoms after hospital discharge compared to 2-month follow-up, indicating that SARS-CoV-2 may transiently impair cognitive function and adversely affect the mood. No improvement in MoCA was observed in 40.5% of the patients at follow-up, indicating possible long-term effects of COVID-19 on global cognitive performance. Medical comorbidities (p = 0.035) significantly predicted the change in MoCA score over time, while fat mass (FM, p = 0.518), Mediterranean diet index (p = .0.944), and Florida Cognitive Activities Score (p = 0.927) did not. These results suggest that the patients’ medical comorbidities at the time of SARS-CoV-2 infection could importantly contribute to the acute impairment of cognitive function and stress the importance of systemic implementation of countermeasures to limit the negative consequences on public health.
Ključne besede: Coronavirus, recovery, acute respiratory sindrom, cognitive functions, cognitive impairment, MOCA, trail-making test
Objavljeno v DiRROS: 01.06.2023; Ogledov: 1760; Prenosov: 807
Celotno besedilo (643,65 KB)
Gradivo ima več datotek! Več... |
