共查询到20条相似文献,搜索用时 15 毫秒
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关于一类时滞人口模型的全局吸引性 总被引:5,自引:0,他引:5
给出了保证时滞人口模型N'(t)=r(t)N(t) t≤0的每一正解N(t)趋于正平衡点 N*=1(t→∞)的一族充分条件.改进了Joseph和Yu的相关结果. 相似文献
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B. R. Crain K. P. Burnham D. R. Anderson J. L. Lake 《Biometrical journal. Biometrische Zeitschrift》1979,21(8):731-748
A nonparametric, robust density estimation method is explored for the analysis of right-angle distances from a transect line to the objects sighted. The method is based on the FOURIER series expansion of a probability density function over an interval. With only mild assumptions, a general population density estimator of wide applicability is obtained. 相似文献
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DANIEL P. WALSH JULIE R. STIVER GARY C. WHITE THOMAS E. REMINGTON ANTHONY D. APA 《The Journal of wildlife management》2010,74(7):1607-1613
Abstract: With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark—resight methods to estimate population size for 2 lekking species: greater sage-grouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowden's estimator and the mixed logit-normal mark—resight model. We captured and marked 75 greater sage-grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage-grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage-grouse daily as they attended 6 leks in 2003 and 3 leks in 2004. Based on our examination of the assumptions of each mark—resight estimator, relative to behavior and biology of these species, we concluded the mixed logit-normal mark—resight model is preferred. We recommend wildlife managers employ mark—resight approaches when statistically rigorous population estimates are required for management and conservation of lekking species. 相似文献
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A. Hamerle 《Biometrical journal. Biometrische Zeitschrift》1988,30(4):471-481
The paper deals with discrete-time regression models to analyze multistate-multiepisode failure time data. The covariate process may include fixed and external as well as internal time dependent covariates. The effects of the covariates may differ among different kinds of failures and among successive episodes. A dynamic form of the logistic regression model is investigated and maximum likelihood estimation of the regression coefficients is discussed. In the last section we give an application of the model to the analysis of survival time after breast cancer operation. 相似文献
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通过引入区域的初始比例因子,考虑了二个区域A与B的封闭种群标记重捕模型,再利用完整的极大似然函数和多项分布函数的性质,给出了当个体在不同区域的个体捕捉率相等时的二个区域之间的转移概率与各区域的初始比例的求法,推导出在不同区域的个体捕捉率不相等但个体低转移率条件下二个区域的封闭种群的标记重捕模型的参数表达式,并用实例说明。 相似文献
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KRISTEN E. RYDING JOSHUA J. MILLSPAUGH JOHN R. SKALSKI 《The Journal of wildlife management》2007,71(1):202-207
Abstract: Assessing the dynamics of wild populations often involves an estimate of the finite rate of population increase (λ) or the instantaneous rate of increase (r). However, a pervasive problem in trend estimation is that many analytical techniques assume independent errors among the observations. To be valid, variance estimates around λ (or r) must account for serial correlation that exists in abundance data. Time series analysis provides a method for estimating population trends and associated variances when serial correlation of errors occurs. We offer an approach and present an example for estimating λ and its associated variance when observations are correlated over time. We present a simplified time series method and variance estimator to account for autocorrelation based on a moving average process. We illustrate the procedure using a spectacled eider (Somateria fischeri) data set of estimated annual abundances from aerial transect surveys conducted from 1957 to 1995. The analytic variance estimator provides a way to plan future studies to reduce uncertainty and bias in estimates of population growth rates. Demographic studies with policy implications or those involving species of conservation concern should especially consider the correlated nature of population trend data. 相似文献
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种群增长的分段指数模型及其参数估计 总被引:4,自引:1,他引:4
本文给出了种群增长的分段指数模型其中N(t)是在时刻t种群的密度,No=N(t0),r0和rl是群群的内禀增长率,t0是转变点,H(t-t0)=1,t≥t0,H(t-t0)=0,t<t0.利用非线性模型的正割法(DUD,Doesn’tusederivatives),可同时确定模型的所有参数(包括交点t0在内).并用于描述长爪沙鼠种群动态. 相似文献
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Logistic方程参数估计中的错误与修正 总被引:2,自引:0,他引:2
Logistic方程在种群生态学研究中被广泛应用,其积分式为N=k/(1+e~(a-rt)),式中e~a=(k-N_0)/N_0。以往对该模型参数的各种估计方法,均将r,K和a作为三个相互独立的参数对待,而与e~a=(K-N_0)/N_0的假设相矛盾。由此估计出的参数K和a使实验初值N_0(t=0时的N值)发生偏离。笔者认为N_0是一个不带随机误差的常数,a值决定于K和N_0,而不是一个独立的参数,因而以往的参数估计方法是错误的,必须予以修正。本文提出了具体的修正方法,即用Marquardt方法或单纯形加速法求参数r和K,然后根据实验初值N_0求a,从而使Logistic微积分方程的共同参数r和K的估计一致。 相似文献
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昆虫种群生态过程的数学模拟,一般以单种种群在不同发育阶段的数量变动为基础。这种模拟研究在国内外已作过很多。但是,如何 相似文献
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Biologists studying short-lived organisms have become aware of the need to recognize an explicit temporal extend of a population
over a considerable time. In this article we outline the concept and the realm of populations with explicit spatial and temporary
boundaries. We call such populations “temporally bounded populations”. In the concept, time is of the same importance as space
in terms of a dimension to which a population is restricted. Two parameters not available for populations that are only spatially
defined characterise temporally bounded populations: total population size, which is the total number of individuals present
within the temporal borders, and total residence time, which is the sum of the residence times of all individuals. We briefly
review methods to estimate these parameters. We illustrate the concept for the large blue butterfly (Maculinea nausithous) and outline insights into ecological and conservation-relevant processes that cannot be gained without the use of the concept. 相似文献
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Estimation of capture probabilities using generalized estimating equations and mixed effects approaches 下载免费PDF全文
Modeling individual heterogeneity in capture probabilities has been one of the most challenging tasks in capture–recapture studies. Heterogeneity in capture probabilities can be modeled as a function of individual covariates, but correlation structure among capture occasions should be taking into account. A proposed generalized estimating equations (GEE) and generalized linear mixed modeling (GLMM) approaches can be used to estimate capture probabilities and population size for capture–recapture closed population models. An example is used for an illustrative application and for comparison with currently used methodology. A simulation study is also conducted to show the performance of the estimation procedures. Our simulation results show that the proposed quasi‐likelihood based on GEE approach provides lower SE than partial likelihood based on either generalized linear models (GLM) or GLMM approaches for estimating population size in a closed capture–recapture experiment. Estimator performance is good if a large proportion of individuals are captured. For cases where only a small proportion of individuals are captured, the estimates become unstable, but the GEE approach outperforms the other methods. 相似文献
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麦蚜复合种群动态预测的Fuzzy推理模式及应用 总被引:1,自引:1,他引:0
本研究利用了山东省曲阜地区1982-1994年共13年的资料,选用了3月下旬至4月上旬平均气温(℃)和4月7上旬温湿系数作为预报因子,麦蚜蚜量始达500(头/丰株)的日期作为预报对象组建Fuzzy推理模式。对历史资料进行回代验证,其历史拟合率达100%。将1995年的观测数据作为独立样本进行试报,预测结果与实际一致。为麦蚜复合种群动态预测提供了一种新的研究方法。 相似文献
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In protein-coding DNA sequences, historical patterns of selection can be inferred from amino acid substitution patterns. High relative rates of nonsynonymous to synonymous changes (=d
N
/d
S
) are a clear indicator of positive, or directional, selection, and several recently developed methods attempt to distinguish these sites from those under neutral or purifying selection. One method uses an empirical Bayesian framework that accounts for varying selective pressures across sites while conditioning on the parameters of the model of DNA evolution and on the phylogenetic history. We describe a method that identifies sites under diversifying selection using a fully Bayesian framework. Similar to earlier work, the method presented here allows the rate of nonsynonymous to synonymous changes to vary among sites. The significant difference in using a fully Bayesian approach lies in our ability to account for uncertainty in parameters including the tree topology, branch lengths, and the codon model of DNA substitution. We demonstrate the utility of the fully Bayesian approach by applying our method to a data set of the vertebrate -globin gene. Compared to a previous analysis of this data set, the hierarchical model found most of the same sites to be in the positive selection class, but with a few striking exceptions. 相似文献
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JOANNE CLAVEL ALEXANDRE ROBERT VINCENT DEVICTOR ROMAIN JULLIARD 《The Journal of wildlife management》2008,72(5):1203-1210
Abstract: A common situation in capture-mark-recapture (CMR) studies on birds and other organisms is to capture individuals not belonging to the studied population only present during the short time of the capture session. Presence of such transient individuals affects demographic parameter estimation from CMR data. Methods exist to reduce biases on survival estimates in the presence of transients and have been shown to be particularly efficient within the Robust Design framework (several secondary capture sessions within a short time interval during which the studied population can be assumed closed). We present a new model to estimate population size accounting for transients. We first used simulated data to show that the method reduces positive biases due to transients. In a second step, we applied the method to a real CMR dataset on a reed warbler (Acrocephalus scirpaceus) population. Population size estimates are reduced by up to 50% when correcting for the presence of transients. Many field studies on managed animal populations use capture-recapture methodology to obtain crucial parameters of the focal population demography. The resulting data sets are used either to estimate population size ignoring the presence of transients, or to estimate vital rates, accounting for transients but overlooking abundance estimation. Our method conciliates these 2 approaches. 相似文献
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Lehmann (1983) provides a detailed discussion on equivariant estimation of the parameters of location, scale and location-scale models. Edwin Prabakaran and Chandrasekar (1994) developed simultaneous equivariant estimation approach and illustrated the method with examples. In this paper, we consider exponential models and obtain minimum risk equivariant estimators of the parameters based on Type II censored samples. The equivariant method of estimation is illustrated with biological and reliability applications. 相似文献