1. Inequalities on the essential joint and essential generalized spectral radiusBrian Lins, Aljoša Peperko, 2024, izvirni znanstveni članek Povzetek: We prove new inequalities for the essential generalized and the essential joint spectral radius of Hadamard (Schur) weighted geometric means of bounded sets of infinite nonnegative matrices that define operators on suitable Banach sequence spaces and of bounded sets of positive kernel operators on $L^2$. To our knowledge the obtained inequalities are new even in the case of singelton sets.
Ključne besede: mathematics, weighted Hadamard-Schur geometric mean, Hadamard-Schur product, essential spectral radius, Haussdorf measure of noncompactness, joint and generalized spectral radius, positive kernel operators, non-negative matrices, bounded sets of operators
Objavljeno v DiRROS: 31.01.2025; Ogledov: 230; Prenosov: 137
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2. Monotonicity properties of weighted geometric symmetrizationsKatarina Bogdanović, Aljoša Peperko, 2024, izvirni znanstveni članek Povzetek: We prove new monotonicity properties for spectral radius, essential spectral radius, operator norm, Hausdorff measure of non-compactness and numerical radius of products and sums of weighted geometric symmetrizations of positive kernel operators on $L^2$. To our knowledge, several proved properties are new even in the finite dimensional case.
Ključne besede: mathematics, weighted Hadamard-Schur geometric mean, Hadamard-Schur product, spectral radius, operator norm, Hausdorff measure of non-compactness, numerical radius, non-negative matrices, positive kernel operators
Objavljeno v DiRROS: 31.01.2025; Ogledov: 236; Prenosov: 130
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4. Extending multivariate sub-quasi-copulasDamjana Kokol-Bukovšek, Tomaž Košir, Blaž Mojškerc, Matjaž Omladič, 2024, izvirni znanstveni članek Povzetek: In this paper, we introduce patchwork constructions for multivariate quasi-copulas. These results appear to be new since the kind of approach has been limited to either copulas or only bivariate quasi-copulas so far. It seems that the multivariate case is much more involved, since we are able to prove that some of the known methods of bivariate constructions cannot be extended to higher dimensions. Our main result is to present the necessary and sufficient conditions both on the patch and the values of it for the desired multivariate quasi-copula to exist. We also give all possible solutions.
Ključne besede: mathematics, multivariate analysis
Objavljeno v DiRROS: 18.06.2024; Ogledov: 643; Prenosov: 364
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5. Evaluating WorldClim version 1 (1961-1990) as the baseline for sustainable use of forest and environmental resources in a changing climateMaurizio Marchi, Iztok Sinjur, Michele Bozzano, Marjana Westergren, 2019, izvirni znanstveni članek Povzetek: WorldClim version 1 is a high-resolution, global climate gridded dataset covering 1961-1990; a ˝normal˝ climate. It has been widely used for ecological studies thanks to its free availability and global coverage. This study aims to evaluate the quality of WorldClim data by quantifying any discrepancies by comparison with an independent dataset of measured temperature and precipitation records across Europe. BIO1 (mean annual temperature, MAT) and BIO12 (mean total annual precipitation, MAP) were used as proxies to evaluate the spatial accuracy of the WorldClim grids. While good representativeness was detected for MAT, the study demonstrated a bias with respect to MAP. The average difference between WorldClim predictions and climate observations was around +0.2 °C for MAT and -48.7 mm for MAP, with large variability. The regression analysis revealed a good correlation and adequate proportion of explained variance for MAT (adjusted R2 = 0.856) but results for MAP were poor, with just 64% of the variance explained (adjusted R2 = 0.642). Moreover no spatial structure was found across Europe, nor any statistical relationship with elevation, latitude, or longitude, the environmental predictors used to generate climate surfaces. A detectable spatial autocorrelation was only detectable for the two most thoroughly sampled countries (Germany and Sweden). Although further adjustments might be evaluated by means of geostatistical methods (i.e., kriging), the huge environmental variability of the European environment deeply stressed the WorldClim database. Overall, these results show the importance of an adequate spatial structure of meteorological stations as fundamental to improve the reliability of climate surfaces and derived products of the research (i.e., statistical models, future projections).
Ključne besede: spatial analysis, spatial interpolation, geostatistics, ecological mathematics
Objavljeno v DiRROS: 20.02.2020; Ogledov: 2412; Prenosov: 1492
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6. Ekstremne korelacijeAnton Cedilnik, 1991, izvirni znanstveni članek Povzetek: In the article we define a quantity which measures the quality of the approximation of a function, given by a table, with a function from a certain family D of nonconstant functions. For this purpose one has to find the infimum and the supremum of the set of correlation coefficients between the given function and functions from D.We do this for the family of all nonconstant functions and for the family of growth functions.
Ključne besede: mathematics, approximations, mathematical programming, forestry, extremal correlation, nonlinear programming
Objavljeno v DiRROS: 12.07.2017; Ogledov: 5218; Prenosov: 2109
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7. O rastnih funkcijahAnton Cedilnik, 1979, izvirni znanstveni članek Povzetek: Članek ima namen z matematičnega stališča osvetliti lastnosti funkcij, ki jih gozdarji, agronomi in biologi uporabljajo za opis rasti nekaterih količin, kot višinska, debelinska, prostorninska rast dreves v odvisnosti od časa in podobno. Navadno uporabljajo za ponazoritev teh procesov elementarne, odsekoma analitične funkcije, ker na takih lahko uporabimo metode aproksimacije eksperimentalnih podatkov. Vendar take funkcije le grobo kažejo dejanska dogajanja v majhnih intervalih neodvisne spremenljivke. Zato bi bilo treba postaviti trdnejše temelje in kriterije za določevanje tipov funkcij, ki bi bile primerne za opisovanje katerih koli pojavov te vrste. Ta študija je poskus v tej smeri.
Ključne besede: matematika, gozdarstvo, rastna funkcija, biološka rast, karakteristična funkcija, subjektivni čas, rast drevesa, mathematics, forestry, growth function, biological growth, characteristic function, subjective time, growth of a tree
Objavljeno v DiRROS: 12.07.2017; Ogledov: 5335; Prenosov: 2158
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8. Prodanova rastna funkcijaAnton Cedilnik, 1983, izvirni znanstveni članek Povzetek: V sestavku so zbrane formule o rastni funkciji ▫$y=x^2/(a+bx+cx^2)$▫ pri poljubni izbiri koeficientov ▫$a,b,c$▫. Dodanih je nekaj napotkov za prilagajanje te funkcije numeričnim podatkom.
Ključne besede: matematika, gozdarstvo, Michail Prodan, rastna funkcija, aproksimacija, mathematics, forestry, Michail Prodan, growth function, approximation
Objavljeno v DiRROS: 12.07.2017; Ogledov: 5382; Prenosov: 2140
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