prediction of seasonal weed seedling emergence patterns is useful in weed management programs. this study was carried out in research fields of islamic azad university – karaj branch in 2009-2010. five crop fields were chosen including: barley, sugar beet and three wheat fields and in each fields between 3 to 5 sites selected randomly. three quadrates were fixed in each sites for studying weeds...

In this paper, we will consider three deterministic models for the study of interaction between human immune system and a virus: logistic model, Gompertz generalized model (or Richards model). A qualitative analysis these based on dynamical systems theory be performed by studying local behavior equilibrium points obtaining dynamics properties from linear stability point view. Additionally, comp...

Three growth models (Richards, Gompertz, and Weibull) were estimated using a computer program employing modified version of the Levenberg-Marquardt approach for solving non-linear regression models. With both small high sample sizes, three data sets collected. The most suitable model studies was added by decomposing into their component parts: additive multiplicative error factors. analysis bas...

Growth, known as the relation between liveweight and age, is explained mathematically by functions that have parameters with biological meaning. These parameters are used to describe growth pattern over time and to estimate the expected weight of animals at specific ages. Animal growth generally follows a sigmoidal pattern and several nonlinear functions have been used to describe it. This stud...

This study compared seven growth models using body weight measurements from 300 progeny obtained from unselected random bred parents. The study which lasted for 20 weeks was carried out at the University of Maiduguri Livestock Teaching and Research farm. R 2 values for the Asymptote regression, Exponential, Gompertz, Logistic, Monomolecular, Richards and Weibull models were 0.994, 0.935, 0.997,...

Tree growth in Korean red pine (Pinus densiflora, hereafter Pd), white koraiensis, Pk), and Japanese larch (Larix kaempferi, Lk) was modeled using Logistic, Korf, Gompertz, Chapman-Richards, Weibull equations stem analysis data from sample trees: 38 trees for Pd, 46 Pk, 45 Lk. The models were fitted to the total increment of tree size variables, diameter at breast height (DBH), height, basal ar...

We defend the hypothesis that life-spanning population survivorship curves, as described by Gompertz' law and composed from cross-sectional data (here mortality), reflect an intrinsic aging principle active in each subject of that population. In other words Gompertz' law reflects aging of a prototypical subject, provided minimal (or no) external causes of death (i.e. fatal infections, starvatio...

This study aimed to fit nonlinear regression models model the growth of characters fruit length (FL) and width (FW) pepper genotypes (Capsicum annuum L.) over time using method ordinary least squares (OLS); identify with best compare it obtained via quantile (QR) in 0.25, 0.5, 0.75 quantiles. Three (Logistic, Gompertz, von Bertalanffy) four quality evaluators were adopted: Akaike information cr...

This study examines the mathematical characteristics of logistic, generalized logistic and Gompertz growth function used in human population analysis. When a is mathematically modeled, it starts with differential equations considered as preliminary study. Then, general solution equation derived. method followed by mathematicians who developed these models. To prepare for study, I framework obje...

The study aimed was to determine the best nonlinear function describing growth stages of Japanese quail breed. To this aim, functions such as exponential, logistic, von Bertalanffy, Brody, and Gompertz were used is in description body weight-age relationship male female quails. Multivariate Adaptive Regression Splines (MARS) data mining algorithm applied individual parameters obtained from dete...