Publikační činnost Katedry aplikované matematiky / Publications of Department of Applied Mathematics (470)

Permanent URI for this collectionhttp://hdl.handle.net/10084/64748

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry aplikované matematiky (470) v časopisech registrovaných ve Web of Science od roku 2003 po současnost.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 323 results

Cardiorespiratory fitness in young and newly diagnosed patients with multiple sclerosis: A cross-sectional study
(Elsevier, 2026) Adamec, Tomáš; Hudeček, Tomáš; Pastucha, Dalibor; Hradílek, Pavel; Kondé, Adéla; Šilarová, Anna
Background Cardiorespiratory fitness (CRF) is impaired in patients with multiple sclerosis (MS) regardless of age, but evidence is limited among young and newly diagnosed patients. The aim of the study is to assess CRF using a maximal exercise test on a treadmill and to examine the relationships between CRF, physical activity level, fatigue, depression, and quality of life (QoL) in young patients newly diagnosed with MS. Methods This cross-sectional study analyzed baseline data from a sample of 43 patients with MS who completed a maximal exercise test on a treadmill, measurement of body composition, and answered the Beck Depression Inventory second edition, modified Fatigue Impact Scale, and 36-item Short Form Survey QoL. Results CRF was significantly lower among patients newly diagnosed with MS (aged 20-45 years) compared to normative values (paired Wilcoxon test, p < 0.001). The median absolute differences between normative values and patients' maximal oxygen uptake (VO(2)max) was 8.5 ml/kg/min (interquartile range [IQR]: 2.4-13.4 ml/kg/min), and the median relative differences was 28.3 % (IQR: 7.1-53.9 %). VO(2)max significantly negatively correlated with fatigue (r(S) = -0.37, p = 0.013), but not depression (r(S) = -0.01, p = 0.971). Significant positive correlations were found between VO(2)max and multiple subscales of QoL, including physical functioning (r(S) = 0.50, p = 0.001), social functioning (r(S) = 0.41, p = 0.007), pain (r(S) = 0.41, p = 0.006), and role limitations due to physical health (r(S) = 0.31, p = 0.047). Conclusion Young patients with newly diagnosed MS already exhibit substantially reduced CRF compared with normative values. Lower VO(2)max is associated with higher fatigue and poorer physical and social aspects of QoL. These findings highlight the need for interventions aimed at improving CRF as an integral component of rehabilitation programs.
Impact of COVID-19 on kidney transplant outcomes: An 8-year study from the Czech Republic
(International Scientific Information, 2025) Roman, Jan; Jalůvka, František; Jelínek, Petr; Ostruszka, Petr; Hrubovčák, Ján; Havránek, Pavel; Kondé, Adéla; Lys, Zdeněk; Drápela, Martin; Procházka, Václav
Background: The Coronavirus disease 2019 (COVID-19) pandemic disrupted transplant programs worldwide. Transplant recipients are especially vulnerable to the effects of SARS-CoV-2 infection due to immunosuppression. This study assessed the impact of the COVID-19 pandemic on kidney transplant outcomes. Material/Methods: We performed a single-center, retrospective cohort study of the kidney transplant program in the Czech Republic. The analysis included 145 recipients transplanted from 138 donors between 2015 and 2022. Cohorts were defined by donor procurement before the pandemic (n=94) or during the pandemic (n=44). The analysis focused on short- and long-term graft and patient outcomes of both groups. Results: No significant differences were found in postoperative kidney graft function (P=0.160) or overall survival before and during the pandemic. The 1- and 3-year survival rates before the pandemic were 96.0% and 90.9%. During the pandemic, they were 97.8% at both time points (P=0.092). Deathcensored failure-free survival was 95.9% and 90.4% at 1 and 3 years before the pandemic versus 95.6% at 1 and 3 years during the pandemic, respectively (P=0.377). Estimated glomerular filtration rate at 7 days (P=0.233) and 1 month (P=0.893) did not differ between vaccinated and non-vaccinated recipients. Conclusions: The COVID-19 pandemic had no significant impact on the short- or long-term outcomes of the kidney transplantation program. These data support sustaining standard kidney transplantation programs during health crises.
Self-reverse labelings of distance magic graphs
(Springer Nature, 2026) Kovář, Petr; Rozman, Ksenija; Šparl, Primož
A graph is distance magic if it admits a bijective labeling of its vertices by integers from 1 up to the order of the graph in such a way that the sum of the labels of all the neighbors of a vertex is independent of a given vertex. We introduce the concept of a self-reverse distance magic labeling of a regular graph which allows for a more compact description of the graph and the labeling in terms of the corresponding quotient graph. We show that the members of several known infinite families of tetravalent distance magic graphs admit such labelings. We present a novel general construction producing a new distance magic graph from two existing ones. Using it we show that for each integer , except for the odd integers up to 19, there exists a connected tetravalent graph of order n admitting a self-reverse distance magic labeling. We also determine all connected tetravalent graphs up to order 30 admitting a self-reverse distance magic labeling. The obtained data suggests a number of natural interesting questions giving several possibilities for future research.
An exact and approximate schur complement method for time-harmonic optimal control problems
(Wiley, 2025) Axelsson, Owe; Lukáš, Dalibor; Neytcheva, Maya
Time-harmonic control problems, constrained by a linear differential equation, can be solved efficiently by utilizing a Fourier time series expansion in the angular frequency variable. Then the optimal solution consists of a series of complex variable space discretization equations, which are uncoupled with respect to the different frequencies. Hence, it suffices to consider a single equation with the angular frequency as a parameter. We consider here methods to solve the so-arising linear system of equations and describe, analyze and test the performance of two novel approaches based on its exact and approximate Schur complement. The performance of the methods is tested and compared with another existing method.
The importance of multimodal CT examination in stroke mimics diagnosis: design of prospective observational multicentre study
(Frontiers Media S.A., 2024) Dvorníková, Kateřina; Kunešová, Veronika; Ely, Marcela; Ostrý, Svatopluk; Čábal, Martin; Reiser, Martin; Machová, Linda; Pavlínová, Markéta; Kondé, Adéla; Eliáš, Pavel; Jonszta, Tomáš; Havelka, Jaroslav; Volný, Ondřej; Bar, Michal
Introduction: Non-contrast computed tomography (CT) and CT angiography are the gold standard in neuroimaging diagnostics in the case of suspected stroke. CT perfusion (CTP) may play an important role in the diagnosis of stroke mimics (SM), but currently, it is not a standard part of the stroke diagnostic procedure. The project is a multicentre prospective observational clinical research focused on refining the diagnostics of stroke and stroke mimics (SM) in hospital care. Aim: This study aimed to evaluate the degree of specificity and sensitivity of multimodal CT (NCCT, CTA, and CTP) in the diagnosis of SM versus stroke. Methodology: In this study, we will include 3,000 patients consecutively admitted to the comprehensive stroke centres with a diagnosis of suspected stroke. On the basis of clinical parameters and the results of multimodal CT and magnetic resonance imaging (MRI), the diagnosis of stroke and SM will be established. To clarify the significance of the use of the multimodal CT scan, the analysis will include a comparison of the blinded results for each imaging scan performed by radiologists and AI technology and a comparison of the initial and final diagnosis of the enrolled patients. Based on our results, we will compare the economic indicators and costs that would be saved by not providing inadequate treatment to patients with SM. Conclusion: The expected outcome is to present an optimised diagnostic procedure that results in a faster and more accurate diagnosis, thereby eliminating the risk of inadequate treatment in patients with SM.
Air pollution, cardiorespiratory fitness and biomarkers of oxidative status and inflammation in the 4HAIE study
(Springer Nature, 2024) Cipryan, Lukáš; Litschmannová, Martina; Barot, Tomáš; Dostál, Tomáš; Šindler, Dominik; Kutáč, Petr; Jandačka, Daniel; Hofmann, Peter
The aim of this study was to investigate the associations between cardiorespiratory fitness (CRF), long-term air pollution exposure and biochemical markers of oxidative status and inflammation. This is a cross-sectional investigation focusing on biochemical markers of oxidative status and inflammation. Participants were Caucasian (N = 1188; age 18-65 years) who lived for at least 5 years in a high air-polluted (Moravian-Silesian; MS) or low air-polluted (South Bohemia; SB) region of the Czech Republic. Healthy runners and inactive individuals were recruited. A multiple regression analysis was used to explain the relationship between multiple independent variables (CRF, trunk fat mass, sex, socioeconomic status, and region (MS region vs. SB region) and dependent variables (oxidative status, inflammation). CRF, trunk fat mass, age and sex significantly predicted almost all selected markers of oxidative status and inflammation (except GSSG, GSH/GSSG and BDNF). Participants living in the MS region presented significantly higher GPx (by 3.1%) and lower BDNF values (by 4.5%). All other investigated biochemical markers were not significantly influenced by region. We did not find meaningful interactions between long-term air-pollution exposure versus markers of oxidative status and inflammation. However, we showed various significant interactions with sex, age, CRF and body composition. The significant association of living in the high air polluted MS region with the BDNF level warrants further attention.
On favorable bounds on the spectrum of discretized Steklov-Poincaré operator and applications to domain decomposition methods in 2D
(Elsevier, 2024) Vodstrčil, Petr; Lukáš, Dalibor; Dostál, Zdeněk; Sadowská, Marie; Horák, David; Vlach, Oldřich; Bouchala, Jiří; Kružík, Jakub
The efficiency of numerical solvers of PDEs depends on the approximation properties of the discretization methods and the conditioning of the resulting linear systems. If applicable, the boundary element methods typically provide better approximation with unknowns limited to the boundary than the Schur complement of the finite element stiffness matrix with respect to the interior variables. Since both matrices correctly approximate the same object, the Steklov-Poincar & eacute; operator, it is natural to assume that the matrices corresponding to the same fine boundary discretization are similar. However, this note shows that the distribution of the spectrum of the boundary element stiffness matrix is significantly better conditioned than the finite element Schur complement. The effect of the favorable conditioning of BETI clusters is demonstrated by solving huge problems by H-TBETI-DP and H-TFETI-DP.
Impact of windfall tax on market dynamics: A Cournot oligopoly model with exogenous shocks
(Elsevier, 2024) Nálepová, Veronika; Lampart, Marek
This study explores the nuanced impact of windfall taxes on market equilibrium, introducing an innovative approach within the Cournot oligopoly framework. The paper uses the 0–1 test for chaos to dissect how profit taxation can stabilize market behaviors under bounded rationality. It suggests that higher taxes may prevent collusion, thereby promoting a more competitive environment. The paper demonstrates that while windfall taxes leave regular markets almost unaffected, they can protect firms in chaotic states from adverse outcomes. This research underscores the necessity for policymakers to tailor windfall tax strategies to specific market conditions, potentially driving enhanced market efficiency. Our insights advocate for the judicious application of windfall taxes, which could significantly shape future economic policies.
On 14-regular distance magic graphs
(Institut Teknologi Bandung, 2024) Kovář, Petr; Krbeček, Matěj
Let G be a graph with n vertices. By N(v) we denote the set of all vertices adjacent to v. A bijection f : V(G) -> {1, 2, ... , n} is a distance magic labeling of G if there exists an integer k such that the sum of labels of all vertices adjacent to v is k for all vertices v in V(G). A graph which admits a distance magic labeling is a distance magic graph. In this paper, we completely characterize all orders for which a 14 -regular distance magic graph exists. Hereby we extended similar results on 2-, 4-, 6-, 8-, 10-, and 12 -regular distance magic graphs.
On the parallel solution of hydro-mechanical problems with fracture networks and contact conditions
(Elsevier, 2024) Stebel, Jan; Kružík, Jakub; Horák, David; Březina, Jan; Béreš, Michal
The paper presents a numerical method for simulating flow and mechanics in fractured rock. The governing equations that couple the effects in the rock mass and in the fractures are obtained using the discrete fracture-matrix approach. The fracture flow is driven by the cubic law, and the contact conditions prevent fractures from self-penetration. A stable finite element discretization is proposed for the displacement-pressure-flux formulation. The resulting nonlinear algebraic system of equations and inequalities is decoupled using a robust iterative splitting into the linearized flow subproblem, and the quadratic programming problem for the mechanical part. The non-penetration conditions are solved by means of dualization and an optimal quadratic programming algorithm. The capability of the numerical scheme is demonstrated on a benchmark problem for tunnel excavation with hundreds of fractures in 3D. The paper's novelty consists in a combination of three crucial ingredients: (i) application of discrete fracture-matrix approach to poroelasticity, (ii) robust iterative splitting of resulting nonlinear algebraic system working for real-world 3D problems, and (iii) efficient solution of its mechanical quadratic programming part with a large number of fractures in mutual contact by means of own solvers implemented into an in-house software library.
Exploring diverse trajectory patterns in nonlinear dynamic systems
(Elsevier, 2024) Lampartová, Alžběta; Lampart, Marek
Describing the dynamical properties of explored systems, one finds the need to distinguish between various types of trajectories. The nature of trajectories is often split into regular and irregular, which will be shown in this paper as too crude. Hence, the main aim of this paper is to give a classification of trajectories reflecting persistence, regularity, chaos, intermittency, and transiency. To depict such phenomena, classical examples from discrete (the Rulkov map) and continuous (the Lorenz system) dynamical systems are applied. In these cases, the maximal Lyapunov exponent, the 0-1 test for chaos, the bifurcation diagram, and the Fourier analysis are applied, and these dynamics characteristics are confronted with trajectory types.
Formation of Ar2+ ions in cold argon plasmas through the ternary recombination mechanism
(IOP Publishing, 2024) Nongni, F. T.; Kalus, René; Benhenni, Malika; Gadéa, Florent Xavier; Yousfi, Mohammed
A general scheme for calculating ternary recombination rate constants of atomic species based on a hybrid quantum-classical nonadiabatic dynamics approach is presented and applied to the specific case of the ternary recombination of atomic ions of argon in cold argon plasmas. Rate constants are reported for both fine-structure states of the Ar + ion,P- 2(3/2) and(2 )P(1/2), T = 300 K, and for selected values of the reduced electric field. A thorough comparison with the literature data available for T = 300 K and a couple of close temperatures is performed with a favorable agreement achieved. It is shown that the excited Ar + ( P-2 (1/2) ) ions may contribute to the formation of dimer ions, Ar-2(+) , as efficiently as the ground-state ions, Ar + (P-2(3/2) ) , due to fast internal conversion of the electronic energy, which takes place in ternary collision complexes, Ar (+) / Ar / Ar .
Solving vibronic dynamics in electron continuum
(American Chemical Society, 2024) Ćosićová, Martina; Dvořák, Jan; Čížek, Martin
We present a general two-dimensional model of conical intersection between metastable states that are vibronically coupled not only directly but also indirectly through a virtual electron in the autodetachment continuum. This model is used as a test ground for the design and comparison of iterative solvers for resonance dynamics in low-energy electron-molecule collisions. Two Krylov-subspace methods with various preconditioning schemes are compared. To demonstrate the applicability of the proposed methods on even larger models, we also test the performance of one of the methods on a recent model of vibrational excitation of CO2 by electron impact based on three vibronically coupled discrete states in continuum (Renner-Teller doublet of shape resonances coupled to a sigma virtual state) including four vibrational degrees of freedom. Two-dimensional electron energy-loss spectra resulting from electron-molecule scattering within the models are briefly discussed.
Ternary recombination of excited Ar+(P1/22) ions, established experimental results reinterpreted with a new extended model
(AIP Publishing, 2024) Nongni, F. T.; Kalus, René; Benhenni, Malika; Gadéa, Florent Xavier; Yousfi, Mohammed
For many years, the recombination of excited ions of argon, Ar+(P1/22), has been assumed negligible under ambient conditions as compared to the recombination of ground-state ions, Ar+(P3/22). This opinion was confronted with detailed experimental results that seem to clearly support it. Here, we propose a new interpretation in light of our recent calculations, which shows that the recombination efficiency is comparable for both fine-structure states. Noteworthily, in our model leading to a picture consistent with the experiment, residual dimer ions emerge from Ar+(P1/22) due to non-adiabatic dynamics effects and interplay in measured data.
Industrial camera model positioned on an effector for automated tool center point calibration
(Springer Nature, 2024) Konečný, Jaromír; Beremlijski, Petr; Bailová, Michaela; Macháček, Zdeněk; Koziorek, Jiří; Prauzek, Michal
The study presents a novel, full model of an industrial camera suitable for robotic manipulator tool center point (TCP) calibration. The authors propose a new solution which employs a full camera model positioned on the effector of an industrial robotic arm. The proposed full camera model simulates the capture of a calibration pattern for use in automated TCP calibration. The study describes an experimental test robot stand for producing a reference data set, a full camera model, the parameters of a generally known camera obscura model, and a comparison of proposed solution with the camera obscura model. The results are discussed in the context of an innovative approach which features a full camera model to assist the TCP calibration process. The results showed that the full camera model produced greater accuracy, a significant benefit not provided by other state-of-the-art methods. In several cases, the absolute error produced was up to seven times lower than with the state-of-theart camera obscura model. The error for small rotation (max. of 5.) and small translation (max. of 20 mm) was 3.65 pixels. The results also highlighted the applicability of the proposed solution in real-life industrial processes.
Robust PRESB preconditioning of a 3-dimensional space-time finite element method for parabolic problems
(De Gruyter, 2024) Foltyn, Ladislav; Lukáš, Dalibor; Zank, Marco
We present a recently developed preconditioning of square block matrices (PRESB) to be used within a parallel method to solve linear systems of equations arising from tensor-product discretizations of initial boundary-value problems for parabolic partial differential equations. We consider weak formulations in Bochner-Sobolev spaces and tensor-product finite element approximations for the heat and eddy current equations. The fast diagonalization method is employed to decouple the arising linear system of equations into auxiliary spatial complex-valued linear systems that can be solved concurrently. We prove that the real part of the system matrix is positive definite, which allows us to accelerate the flexible generalized minimal residual method (FGMRES) by the PRESB preconditioner. The action of PRESB on a vector includes two solutions with positive definite matrices. The spectrum of the preconditioned system lies between 1/2 and 1. Finally, we combine the PRESB-FGMRES method with multigrid-CG iterations and illustrate the numerical efficiency and the robustness for spatial discretizations up to 12 millions degrees of freedom.
L1CAM is not a predictive factor in early-stage squamous-cell cervical cancer
(International Institute of Anticancer Research, 2023) Romanová, Martina; Židlík, Vladimír; Javůrková, Veronika; Kondé, Adela; Šimetka, Ondřej; Klát, Jaroslav
Aim: Our study aimed to assess expression of L1 cell adhesion molecule (L1CAM) in early-stage cervical squamous-cell cancer as a prognostic factor. Patients and Methods: This retrospective, single-institution study included 154 patients who underwent radical hysterectomy for early-stage squamous cell cervical cancer between 2007 and 2017. Tumor samples from 154 patients were available for L1CAM analysis by immunohistochemistry. Among all patients, radical abdominal hysterectomy was performed in 144 cases. Results: L1CAM expression was positive in 24 tumors (15.6%) of the whole group. In relation to the grade of differentiation and the presence of lymphovascular invasion, L1CAM expression did not show an association (p=0.154 and p=0.306, respectively). The disease-free interval and overall survival also did not significantly differ between L1CAM-positive and L1CAM-negative cases (p=0.427 and p=0.240, respectively). For histopathological characteristics, L1CAM-positive cases had a significantly higher median tumor size (p=0.015). Even in the selected group of 115 cases without nodal infiltration, L1CAM status had no effect on the relapse rate during follow-up. Conclusion: Our study did not confirm the results of previous studies showing L1CAM expression to be a negative prognostic factor in cervical cancer. In our study, increased L1CAM expression in early-stage squamous-cell cervical cancer was not associated with adverse prognosis regarding disease recurrence, disease-free survival, nor overall survival. L1CAM expression was correlated only with the size of the tumor.
Time-dependent unavailability exploration of interconnected urban power grid and communication network
(MDPI, 2023) Vrtal, Matěj; Fujdiak, Radek; Benedikt, Jan; Praks, Pavel; Briš, Radim; Ptáček, Michal; Toman, Petr
This paper presents a time-dependent reliability analysis created for a critical energy infrastructure use case, which consists of an interconnected urban power grid and a communication network. By utilizing expert knowledge from the energy and communication sectors and integrating the renewal theory of multi-component systems, a representative reliability model of this intercon nected energy infrastructure, based on real network located in the Czech Republic, is established. This model assumes reparable and non-reparable components and captures the topology of the inter connected infrastructure and reliability characteristics of both the power grid and the communication network. Moreover, a time-dependent reliability assessment of the interconnected system is provided. One of the significant outputs of this research is the identification of the critical components of the interconnected network and their interdependencies by the directed acyclic graph. Numerical results indicate that the original design has an unacceptable large unavailability. Thus, to improve the reliability of the interconnected system, a slightly modified design, in which only a limited number of components in the system are modified to keep the additional costs of the improved design limited, is proposed. Consequently, numerical results indicate reducing the unavailability of the improved interconnected system in comparison with the initial reliability design. The proposed unavailability exploration strategy is general and can bring a valuable reliability improvement in the power and communication sectors.
Metaphors of distance, size and temperature in sociometry of small social groups: A generalizability theory approach
(Springer Nature, 2023) Kundrát, Josef; Rečka, Karel; Litschmannová, Martina; Vrtková, Adéla; Baumgartner, František; Benešová, Tereza; Paulík, Karel; Skanderová, Lenka; Fabián, Tomáš; Beranová, Helena; Ullmannová, Dominika
We have developed a new interactive instrument that uses psychological distance (represented by visual distance) together with the metaphors of size and temperature to assess liking and infuence among primary school students. To test its concurrent validity, we compare its results with an established sociometric instrument. Further more, we examine the characteristics of the obtained ratings, the main sources of variability of the observed ratings, and the reliability of person-level results. Our results indicate that the ratings derived from the interactive visual metaphors of dis tance, size, and temperature show adequate reliability and strongly correlate with a traditional sociometric inventory that uses rating scales. The novelty of our approach lies in the use of generalizability theory, which allows for the decomposition of obtained ratings into class, rater, rated person, dyadic, and idiosyncratic efects. This allows for a more nuanced analysis of the relationships between members of social groups, such as school classes.
Expecting the unexpected: Entropy and multifractal systems in finance
(MDPI, 2023) Orlando, Giuseppe; Lampart, Marek
Entropy serves as a measure of chaos in systems by representing the average rate of information loss about a phase point’s position on the attractor. When dealing with a multifractal system, a single exponent cannot fully describe its dynamics, necessitating a continuous spectrum of exponents, known as the singularity spectrum. From an investor’s point of view, a rise in entropy is a signal of abnormal and possibly negative returns. This means he has to expect the unexpected and prepare for it. To explore this, we analyse the New York Stock Exchange (NYSE) U.S. Index as well as its constituents. Through this examination, we assess their multifractal characteristics and identify market conditions (bearish/bullish markets) using entropy, an effective method for recognizing fluctuating fractal markets. Our findings challenge conventional beliefs by demonstrating that price declines lead to increased entropy, contrary to some studies in the literature that suggest that reduced entropy in market crises implies more determinism. Instead, we propose that bear markets are likely to exhibit higher entropy, indicating a greater chance of unexpected extreme events. Moreover, our study reveals a power-law behaviour and indicates the absence of variance.

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