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1.
采用有限空间种群增长的逻辑斯谛模型探讨格氏栲种群基面积增长规律.提出自适应通用模型ds/dt=rs(1-sθ/kφ).该模型包括Logistic模型、Smith模型、Gompertz模型、崔Lawson模型和ZLogistic模型;运用改进单纯形对自适应通用模型进行优化,拟合结果比Logistic模型更符合格氏栲种群实际增长趋势,增长速度最大是在147年.  相似文献   

2.
论Richards增长曲线   总被引:5,自引:0,他引:5  
本文给出了Richards增长曲线一个很好的解析表达式,它使得Logistic增长曲线、Gompertz增长曲线与Richards增长曲线之间的关系清晰了,提示了著名的Logistic增长曲线与Gompertz增长曲线是Richards增长曲线的特殊情形,而且还给出了Richards增长曲线一些很好的特性。  相似文献   

3.
珍稀濒危植物青钩栲种群数量特征研究   总被引:20,自引:2,他引:18  
提出自适应种群增长新模型S=exp(aln^2(1+ce^-rt)+βln(1+ce^-et)+γ),该模型包融了Logistic模型、Smith模型、Gompertz模型、崔-Lawson模型、张-Logistic模型和刘-Logistic模型,运用遗传算法适应新模型进行参数估计,拟合青钩栲种群增长规律比其它种群增长模型更符合青钩栲群种的实际增长趋势,说明新模型具有一定的实用价值。  相似文献   

4.
三种模型对动物细胞生长模拟的比较   总被引:3,自引:0,他引:3  
用 Monod方程、Logistic方程和一个简单的结构模型来模拟批式培养动物细胞的生长。结果显示Moned方程和Logistic方程都不能很好拟合延迟期细胞的生长,而结构模型可以描述细胞从延迟期到静止期的生长过程。  相似文献   

5.
三次设计结合模矢法拟合Logistic曲线的研究   总被引:5,自引:0,他引:5  
Logistic曲线是种群动态的一个经典模型,针对传统拟合方法存在的缺陷和三次设计的优点,以及拟合过程是离差平方和最小──可看作是运筹学中无约束极值问题──的优化原则,本文提出新的方法-三次设计结合模大法的组合方法来拟合,结果表明该法能取长补短,拟合效果最佳,因此在一般非线性模型参数求解中具有普遍意义.  相似文献   

6.
对5个不同纬度来源的野生大豆(Glycinesoja)、栽培大豆(Glycinemas)和半野生大豆进行同地移栽和分期播种实验表明,1年生野生大豆的拟种群的3类组元动态均符合Logistic增长规律,参数r与纬度呈正相关,参数K受环境饰变影响.拟种群动态拟合参数r与个体的生殖力呈正相关,证实植物拟种群动态具有重要的生态适应意义.  相似文献   

7.
窦薇  宛新荣 《兽类学报》2000,20(3):212-216
通过对Richards方程数学属性的分析表明,该方程具有变动的拐点值,因而在描绘兽类多种多样的生长过程时具有良好的可塑性。依据其方程参数n取植的不同,Richards方程包含了Spillman,Logistic,Gompertz以及Bertalanffy方程。为了评估Richards方程对兽类生长过程的拟合优度,作引用10组哺乳动物兽类生长数据,将它与一些经典的生长模型如Spillman,Log  相似文献   

8.
1993年10月-1995年5月室内饲养东方田鼠的结果显示:幼鼠3日龄耳壳安全直立,4日龄能辨雌雄,8日龄披毛长全,8-10日龄睁眠,10日龄左右牙齿长全,15-20日龄可独立生活。冬季出生的约2个月性成熟,春季出生珠约50天性成熟。其体重生长曲线珂用Logistic曲线方程进行拟合。  相似文献   

9.
本文讨论中立型 Logistic方程组的所有关于它的正平衡点振动的正解的充分条件。  相似文献   

10.
松突圆蚧种群动态研究   总被引:9,自引:0,他引:9  
对松突圆蚧为害时间不同的两个调查区的松突圆蚧种群动态进行调查,建立了相应的数学模型.对松突圆蚧种群的全年种群波动规律运用带时滞效应的Logistic模型进行拟合,通过内禀增长率r和时滞τ的拟合值对种群出现的周期性波动作出解释.  相似文献   

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13.
Models of HIV-1 infection that include intracellular delays are more accurate representations of the biology and change the estimated values of kinetic parameters when compared to models without delays. We develop and analyze a set of models that include intracellular delays, combination antiretroviral therapy, and the dynamics of both infected and uninfected T cells. We show that when the drug efficacy is less than perfect the estimated value of the loss rate of productively infected T cells, delta, is increased when data is fit with delay models compared to the values estimated with a non-delay model. We provide a mathematical justification for this increased value of delta. We also provide some general results on the stability of non-linear delay differential equation infection models.  相似文献   

14.
Using linear and non-linear regression to fit biochemical data   总被引:7,自引:0,他引:7  
For biochemists or chemists the most common form of data analysis is likely to be regression analysis. This is a technique to find the ‘best’ values for various experimental parameters; defined as those values which, when used in an appropriate equation, result in the minimum deviation of the calculated results from the experimental data. Despite the widespread application of regression analysis, the basis of the technique and the underlying assumptions are often poorly understood or appreciated. This article describes the basics of linear and non-linear regression, the role of ‘weighting’ and the potential pitfalls of such analyses.  相似文献   

15.
Permeability controls the fluid flow into and out of soft tissue, and plays an important role in maintaining the health status of such tissue. Accurate determination of the parameters that define permeability is important for the interpretation of models that incorporate such processes. This paper describes the determination of strain-dependent permeability parameters from the nonlinear biphasic equation from experimental data of different sampling frequencies using the Nelder-Mead simplex method. The ability of this method to determine the global optimum was assessed by constructing the whole manifold arising from possible parameter combinations. Many parameter combinations yielded similar fits with the Nelder-Mead algorithm able to identify the global maximum within the resolution of the manifold. Furthermore, the sampling strategy affected the optimum values of the permeability parameters. Therefore, permeability parameter estimations arising from inverse methods should be utilised with the knowledge that they come with large confidence intervals.  相似文献   

16.
单纯形加速法拟合生态学中的非线性模型   总被引:6,自引:0,他引:6  
本文以Logistic模型,Taylor幂法则模型,Holling功能反应模型,以及种群内禀增长力Rm等模型的拟合和参数估计为例,探讨单纯形加速法在生态模型优化拟合和参数估计中的应用.结果表明,单纯形加速法拟合生态学中的非线性模型不仅适用广泛,而且拟合过程是直接求原来非线性模型的最优拟合,因而优于生态学中通常使用的将原模型“线性化后再拟合”的方法,而与其它一些最优化方法,如:麦夸方法、枚举选优法等比较,由于单纯形法不需计算目标函数的偏导数,因而计算不受目标函数及其偏导函数复杂程度的限制,而且对于各种模型其求优计算过程十分相似,可以编制统一的计算程序.本研究所编制的计算机程序对于本文未提到的其它一些模型也是完全适用的,在应用时仅需修改定义目标函数的自定义函数语句即可.研究也发现,在求优过程中,只要搜索系数选择适当和实际数据合理,是可以保证寻优成功的.  相似文献   

17.
Several non-linear reaction networks are analyzed in order to study the influence of time hierarchy on the dynamics of biochemical systems. The analysis is based on the assumption that the separation of the time constants within metabolic systems is a direct consequence of strong differences of enzyme concentrations. Therefore, as variable system parameters, only the enzyme concentrations are considered. By investigation of the stationary states of various three-component models with feedback-activation bifurcation diagrams within a two-dimensional parameter space, the enzyme simplex, are constructed. The diagrams contain the information about the number of stationary states, their stability properties as well as the type of motion expected at different parameter combinations. The results support the hypothesis that systems with separated time constants generally show a simple dynamic behaviour. Complex motions can be expected mainly for systems without time hierarchy, which are characterized by parameters located within the centre of the enzyme simplex. Quantitative measures for the time hierarchy and the complexity of the dynamics are derived. It is supposed that the separation of time constants is a main feature of the evolution of biochemical systems. The hypothesis is further supported by the consideration of the time hierarchy of the glycolytic pathway.  相似文献   

18.
Anaerobic waste water treatment processes are commonly presented by the fifth order Hill and Barth non-linear model, describing three main stages of anaerobic digestion. The model investigated in the present work is a modified version of the Hill and Barth model, which includes substrate inhibition of growth of methanogenic bacteria. Parameter estimation of this model is a difficult problem because of the high number of parameters to be estimated and the rather restricted information concerning the variables. The aim of the present work is to use sensitivity theory to find a method for selecting the most significant parameters. In particular, we develop a sensitivity model for anaerobic digestion using relative sensitivity functions. Simulation results from the sensitivity model show that the number of parameters to be estimated can be reduced from 12 to 4. We suggest a 2-step procedure for parameter estimation, which is also based on sensitivity analysis. This procedure gives results, which allow for off-line determination of parameter values if the experimental data for biogas production rate are known.  相似文献   

19.
The present work concerns a quantitative analysis of parameters that affect apparent blood viscosity at different low shear rates, i.e, between 1 s−1 and, 100 s−1. Viscosity profile of a large number of blood samples from thromboembolic stroke cases and age and sex matched healthy controls were studied which confirmed non-Newtonian power law behaviour of blood. The power law coefficients,n andk, which are unique to each blood sample, were related with blood viscosity parameters in the form of a mathematical equation by performing non-linear regression analysis. It was possible to calculaten andk of power law model by supplying the values of major blood constituents in the equation obtained for stroke and controls. The calculation ofn andk of a blood sample using the equation obtained, provided a quick information on its apparent viscosity values at any given shear rate without viscometry. The calculated and the experimental viscosity were found in good agreement within a permissible error range. The relation obtained between power law coefficients and major blood constituents in the present investigation would give a quantification of different blood viscosity parameters contributing to the resistance to flow of blood. Such an analysis may be considered as a scientific basis for the study of blood fluidity in different disease conditions.  相似文献   

20.
We re-examined data for field metabolic rates of varanid lizards and marsupial mammals to illustrate how different procedures for fitting the allometric equation can lead to very different estimates for the allometric coefficient and exponent. A two-parameter power function was obtained in each case by the traditional method of back-transformation from a straight line fitted to logarithms of the data. Another two-parameter power function was then generated for each data-set by non-linear regression on values in the original arithmetic scale. Allometric equations obtained by non-linear regression described the metabolic rates of all animals in the samples. Equations estimated by back-transformation from logarithms, on the other hand, described the metabolic rates of small species but not large ones. Thus, allometric equations estimated in the traditional way for field metabolic rates of varanids and marsupials do not have general importance because they do not characterize rates for species spanning the full range in body size. Logarithmic transformation of predictor and response variables creates new distributions that may enable investigators to perform statistical analyses in compliance with assumptions underlying the tests. However, statistical models fitted to transformations should not be used to estimate parameters of equations in the arithmetic domain because such equations may be seriously biased and misleading. Allometric analyses should be performed on values expressed in the original scale, if possible, because this is the scale of interest.  相似文献   

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