Journal ArticleDOI
Generalization and Reparameterization of Some Sigmoid and Other Nonlinear Functions
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In this paper, the Pearl-Reed function is used to locate a point of inflection free from the effects of two additional parameters specifying the manner in which the function approaches its asymptotes.Abstract:
Many functions previously employed in describing growth plhenoimlena can Inow be included in a single new function obtained principally by raising to a power the difference between a weighted elementary functioni and its exponiential raised to another power. Furthermore, new parameters for the simplest two-asymptote, third-degree form of the well-known Pearl-Reed function can be specified so as to locate a point of inflection free from the effects of two additional parameters specifying the manner in which the function approaches its asymptotes. Convenient expressions for derivatives and partial derivatives of all the inew functions and the locationis of points of inflection in terms of the new parameters are given to help interested scientists in preparing short FORTRAN or ALGOL subroutines for use with existiIng computer programs, and in making close initial estimates of parameters so that convergence of iterative solutions will be more likely.read more
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Journal ArticleDOI
Analysis of growth equations.
TL;DR: In this article, the authors show that the growth path of a tree is inherently imprecise and can be viewed as a wide valley rather than a single line, and that growth expansion is proportional to current tree size.
Book
Modeling Forest Trees and Stands
TL;DR: In this paper, even-aged stands are modeled as whole-stands and size-class models for Even-aged Stands are used to evaluate individual-tree stand density.
Journal ArticleDOI
Hypothesis Testing in Ecology: Psychological Aspects and the Importance of Theory Maturation
TL;DR: Problem areas in ecology are examined in light of consideations, including failure to publish negative results, misuses of mathematical models, confusion resulting from ambiguous terms (such as "diversity" and "niche"), and biases against new ideas.
Book ChapterDOI
The role of Thiobacillus ferrooxidans in hydrometallurgical processes
TL;DR: In this paper, the authors illustrate the increased interest which is manifested in the microorganisms, Thiobacillus ferrooxidans, involved in the biohydrometallurgical extraction processes.
Journal ArticleDOI
Comparison of three cold hardiness tests for conifer seedlings
TL;DR: Greenhouse-cultured, container-grown ponderosa pine, interior Douglas-fir, and Engelmann spruce were cold acclimated and deacclimated in growth chambers over 19 weeks and cold hardiness was measured weekly by a whole-plant freeze test and by two quick tissue tests: freeze-induced electrolyte leakage of needles, and differential thermal analysis of buds.
References
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Journal ArticleDOI
The Gompertz Curve as a Growth Curve
TL;DR: Benjamin Gompertz showed that if the average exhaustions of a man's power to avoid death were such that at the end of equal infinitely small intervals of time, he lost equal portions of his remaining power to oppose destruction, then the number of survivors at any age x would be given by the equation.
Journal ArticleDOI
A Trend Line for Growth Series
TL;DR: In this paper, the authors present a trend line for growth series, which is based on the trend line of the growth of the United States in the last decade of the 20th century.