636 research outputs found
Analytical representation of ellipses in the Aitchison geometry and its application
No full textsummary:Compositional data, multivariate observations that hold only relative information, need a special treatment while performing statistical analysis, with respect to the simplex as their sample space ([Aitchison, J.: The Statistical Analysis of Compositional Data. Chapman and Hall, London, 1986.], [Aitchison, J., Greenacre, M.: Biplots of compositional data. Applied Statistics 51 (2002), 375–392.], [Buccianti, A., Mateu-Figueras, G., Pawlowsky-Glahn, V. (eds): Compositional data analysis in the geosciences: From theory to practice. Geological Society, London, Special Publications 264, 2006.], [Filzmoser, P., Hron, K.: Outlier detection for compositional data using robust methods. Math. Geosci. 40 (2008), 233–248.], [Filzmoser, P., Hron, K.: Correlation analysis for compositional data. Math. Geosci., to appear.], [Filzmoser, P., Hron, K., Reimann, C.: Principal component analysis for compositional data with outliers. Environmetrics, to appear.], [Filzmoser, P., Hron, K., Reimann, C., Garrett, R.: Robust factor analysis for compositional data. Computers & Geosciences, to appear.], [Pearson, K.: Mathematical contributions to the theory of evolution. On a form of spurious correlation which may arise when indices are used in the measurement of organs. Proceedings of the Royal Society of London 60 (1897), 489–502.]). For the logratio approach to the statistical analysis of compositional data the so called Aitchison geometry was introduced and confirmed to be the meaningful one. It was shown in [Egozcue, J. J., Pawlowsky-Glahn, V.: Simplicial geometry for compositional data. In: Buccianti, A., Mateu-Figueras, G., Pawlowsky-Glahn, V., (eds): Compositional data analysis in the geosciences: From theory to practice. Geological Society, London, Special Publications 264 (2006), 145–160.], [Pawlowsky-Glahn, V., Egozcue, J. J., Tolosana-Delgado, J.: Lecture notes on compositional data analysis. http://hdl.handle.net/10256/297, 2007.] that it is quite easy to express simple geometric objects like compositional lines, this is however not the case for ellipses, although they play a fundamental role within most statistical methods, for example in outlier detection ([Filzmoser, P., Hron, K.: Outlier detection for compositional data using robust methods. Math. Geosci. 40 (2008), 233–248.]). The aim of the paper is to introduce a way, based on coordinate representations of compositions, how to obtain an analytical representation of ellipses in the Aitchison geometry
Nonnewtonian fluid flow simulation using lattice Boltzmann method
No full textTitle: Non-newtonian fluid flow simulation using lattice Boltzmann method Author: Bc. Pavel Kuriščák Department: Mathematical Institute, Charles University Supervisor: RNDr. Ing. Jaroslav Hron Ph.D. Supervisor's e-mail address: [email protected] Abstract: The aim of this thesis is to find and estabilish a modification to the Lattice Boltzmann Method, allowing it to simulate non-newtonian behaviour of fluids. In the theoretical part of thesis, there is introduced a derivation, based on the work of [22], that is capable of arriving to macroscopical Navier-Stokes equa- tions completely a priori from the Boltzmann equation, utilizing the Hermite basis expansion. This derivation is afterwards applied to the method suggested by [11], that uses the changed equilibrium distribution to fine-tune the local fluid viscosity according to the non-newtonian model. In the last part of thesis, this method is implemented in the form of lattice kinetic scheme and tested on three sample problems. Keywords: Lattice Boltzmann Method, non-newtonian fluids, Hermite expansion, lattice kinetic schem
Mapping of the Eurasian otter (Lutra lutra L.) in the Hron River basin (Slovakia)
No full textIn: Zoologické dny Brno 2025 : sborník abstraktů z konference. 1. vyd. Brno : Ústav biologie obratlovců AV, 2025. ISBN 978-80-87189-47-4. S. 229-229.Hron is the second longest river in Slovakia. It springs under Kráľová hoľa at an altitude of 934 m and flows into the Danube not far from the place where the Danube leaves the territory of Slovakia. Mapping the river otter in a square grid is, despite the reservations, a method used to determine the spread of this species over a relatively large area and its changes. The distribution of the otter in the Hron river basin was investigated during five field mappings (winter 1995/1996, summer and autumn 2010, winter 2011/2012, winter 2021/2022, winter 2022/2023) using a modified IUCN/OSG standard method. It was about the evidence of the presence of a species, or its residence signs on selected 600 m sections of streams in the network of 48 squares of the Databank of the Fauna of Slovakia (approx. 10 × 12 km) and their 150 quadrants (approx. 2.5 × 3 km). During the first mapping in the winter of 1995/1996, the lowest number of positive squares (35; t. j. 72,9 %) and quadrants (71; 47,3 %) was recorded. Signs of otter habitat were mainly absent in the lower reaches of the Hron, but they were found near its mouth into the Danube, or on some tributaries of the lower Hron (e.g. Paríž). During further mapping, there was an increase in both positive squares and quadrants in the entire river basin. The increase was most pronounced in the middle and lower part of the basin. The highest number of positive squares (46; 95,8 %) and quadrants (125; 83,3 %) was recorded in the winter of 2021/2022.VEGA 1/0836/08 Stanovištné nároky vydry riečnej (Lutra lutra L.) na vodných tokoch
VEGA 01/0762/09 Ekologická integrita krajiny a hodnotenie jej zmien v kultúrnej krajine vo vzťahu k ochrane biodiverzity a k udržateľnému rozvoju v období globálnej klimatickej zmeny
KEGA 036UMB-4/2018 Súčasná a systémová ekológia: štruktúra, dynamika a komplexita spoločenstiev a ekosystémov
VEGA 003UMB-4/2023 Koncepty a metódy monitoringu živočíchov v ochrane prírod
Simplicial principal component analysis for density functions in Bayes spaces
No full textProbability density functions are frequently used to characterize the distributional properties
of large-scale database systems. As functional compositions, densities primarily carry
relative information. As such, standard methods of functional data analysis (FDA) are not
appropriate for their statistical processing. The specific features of density functions are
accounted for in Bayes spaces, which result from the generalization to the infinite dimensional
setting of the Aitchison geometry for compositional data. The aim is to build up a
concise methodology for functional principal component analysis of densities. A simplicial
functional principal component analysis (SFPCA) is proposed, based on the geometry
of the Bayes space B2 of functional compositions. SFPCA is performed by exploiting the
centred log-ratio transform, an isometric isomorphism between B2 and L2 which enables
one to resort to standard FDA tools. The advantages of the proposed approach with respect
to existing techniques are demonstrated using simulated data and a real-world example of
population pyramids in Upper Austria
A robust Parafac model for compositional data
No full textA robust Tucker3 model for three-way compositional data is presented. The algorithm to compute the Tucker3 parameters is based on ALS procedure implemented with robust alternative measures as Comedian and correlation median. The algorithm is able to capture the features of the complex structure, avoiding the information loss problem that occurs when two-way analysis techniques are adopted and the outliers effects. Some evidences are illustrated performing the model to macroeconomic compositional data
Efficient methods for visualization of volumetric data
No full textTitle: Efficient methods for visualization of volumetric data Author: Martin Holeček Department: Mathematical Institute of Charles University Supervisor: RNDr. Ing. Jaroslav Hron, Ph.D., Mathematical Institute Abstract: The aim is to make an overview of and present implementation usefull for rendering of simulated datasets and CT and MR datasets. We will examine the methods of direct volume rendering of structured and unstructured grids and head to meaningful simultaneous realtime rendering of both types. In the first part, we briefly present the development, problems and targets of the field. Next, based on knowledge about existing algorithms, we choose one solution and present our own implementation and modification of algorithms. In detail, the object of our study will be numerical solutions of volume rendering integral by preintegration and paralelization of the process of projecting tetrahedra and perspective correction. For practical reasons we focus on the efficiency, that means computation time, used memory and usefullnes for medical presentation. The results will be compared with some other existing implementations. Keywords: volume rendering, preintegration, unstructured gri
Characterization of solid-fluid mixtures
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 59-65).Issued also on microfiche from Lange Micrographics.In this work we develop and investigate a mathematical model for the description of the mechanical behavior of soft, hydrated tissues with significant perfusion. We set up and derive the mathematical description and balance laws using the continuum mixture theory as the theoretical framework. The constitutive relations suitable to describe perfumed soft tissue and appropriate bounder conditions are discussed in terms of its possible determination from experimental data. We solve illustrative steady, one and two dimensional problems of disunion through snidely deformed slab, and develop and implement appropriate numerical schemes. The main focus is on developing an algorithm based on finite elements for finding approximate solution to the continuous, nonlinear, steady, two dimensional problem
Tabulaephorus Arenberger 1993
No full textTabulaePhorus marPtys (Christoph, 1873) Material examined. 1 ♂, 1 ♀ (CUK), Kyzyl, 14.–15.vi.2001, P. Ustjuzhanin; 1 ♂ (CRS), Moren, 4.–5.vi.2004, J.Hron, M. Cesanek & J. Rekelj; 3 ♂ (CRS, CUK), Ondum, 12.vi.2004, J. Hron, M. Cesanek & J. Rekelj; 1 ♂ (CUK), 1 ♀, Dus Dag, 19.vi.2004, J. Hron, M. Cesanek & J. Rekelj; 2 ♂ (CRS), Barlyk, 26.vi.2004, J. Hron, M. Cesanek & J. Rekelj. Distribution. South European Russia, Kazakhstan, Altai, Tuva, Mongolia, China.Published as part of Ustjuzhanina, Anna, 2017, Pterophoridae (Lepidoptera) fauna of the Republic of Tuva, pp. 317-328 in Zootaxa 4319 (2) on page 327, DOI: 10.11646/zootaxa.4319.2.3, http://zenodo.org/record/88913
Low-mass lithium-rich AGB stars in the Galactic bulge: evidence for cool bottom processing?
No full text- …
