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Iskalni niz: "ključne besede" (mathematics) .

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1.
O rastnih funkcijah
Anton Cedilnik, 1979

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
DiRROS - Objavljeno: 12.07.2017; Ogledov: 1243; Prenosov: 253
URL Celotno besedilo (0,00 KB)
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2.
Prodanova rastna funkcija
Anton Cedilnik, 1983

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
DiRROS - Objavljeno: 12.07.2017; Ogledov: 1262; Prenosov: 257
URL Celotno besedilo (0,00 KB)
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3.
Ekstremne korelacije
Anton Cedilnik, 1991

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
DiRROS - Objavljeno: 12.07.2017; Ogledov: 1279; Prenosov: 270
URL Celotno besedilo (0,00 KB)
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4.
Evaluating WorldClim version 1 (1961-1990) as the baseline for sustainable use of forest and environmental resources in a changing climate
Maurizio Marchi, Iztok Sinjur, Michele Bozzano, Marjana Westergren, 2019

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
DiRROS - Objavljeno: 20.02.2020; Ogledov: 239; Prenosov: 146
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