For approximation of some well-known time series of Paramecia caudatun population dynamics (G. F. Gause, The Struggle for Existence, 1934) Verhulst and Gompertz models were used. The parameters were ...estimated for each of the models in two different ways: with the least squares method (global fitting) and non-traditional approach (a method of extreme points). The results obtained were compared and also with those represented by G. F. Gause. Deviations of theoretical (model) trajectories from experimental time series were tested using various non-parametric statistical tests. It was shown that the least square method-estimations lead to the results which not always meet the requirements imposed for a "fine" model. But in some cases a small modification of the least square method-estimations is possible allowing for satisfactory representations of experimental data set for approximation.
•Fitting of time series on larch bud moth dynamics.•Moran–Ricker models with time lags.•Asymptotic dynamic regimes.
Modifications of Moran–Ricker model with time lags are applied for fitting of larch ...bud moth (Zeiraphera diniana Gn.) time series. Model parameters were estimated, and deviations between model trajectories and empirical time series were analyzed with various statistical tests. It was shown that some of considered models allowed obtaining rather good fitting. For estimated parameters asymptotic stable dynamic regimes were found: it is 9-year cycle (for model with time lag in four years), it is 18-year cycle (with close values of cycle coordinates for model with time lag in one year), or regime with complicated dynamics (for model with time lag in three years). Obtained results correspond to biological imagination about fluctuations of larch bud moth populations.
A stochastic model of migrations on a lattice and with discrete time is considered. It is assumed that space is homogenous with respect to its properties and during one time step every individual ...(independently of local population numbers) can migrate to nearest nodes of lattice with equal probabilities. It is also assumed that population size remains constant during certain time interval of computer experiments. The following variants of estimation of encounter rate between individuals are considered: when for the fixed time moments every individual in every node of lattice interacts with all other individuals in the node; when individuals can stay in nodes independently, or can be involved in groups in two, three or four individuals. For each variant of interactions between individuals, average value (with respect to space and time) is computed for various values of population size. The samples obtained were compared with respective functions of classic models of isolated population dynamics: Verhulst model, Gompertz model, Svirezhev model, and theta-logistic model. Parameters of functions were calculated with least square method. Analyses of deviations were performed using Kolmogorov-Smirnov test, Lilliefors test, Shapiro-Wilk test, and other statistical tests. It is shown that from traditional point of view there are no correspondence between the encounter rate and functions describing effects of self-regulatory mechanisms on population dynamics. Best fitting of samples was obtained with Verhulst and theta-logistic models when using the dataset resulted from the situation when every individual in the node interacts with all other individuals.
Data on cross sections for the reaction
238
U(
γ,F
) in the giant-resonance region were analyzed in connection with the preparation of new experiments aimed at studying
238
U photofission—in ...particular, in beams of photons from in-flight positron annihilation on internal targets of positron storage rings. These data were taken from measurements also performed with annihilation photons but from positron beams external to the accelerators used. The procedures applied in such measurements and based both on processing the multiplicity of detected neutrons and on detecting fission fragments were also analyzed.
The applicability of discrete mathematical models for the description of diamondback moth (DBM) (Plutella xylostella L.) population dynamics was investigated. The parameter values for several ...well-known discrete time models (Skellam, Moran–Ricker, Hassell, Maynard Smith–Slatkin, and discrete logistic models) were estimated for an experimental time series from a highland cabbage-growing area in eastern Kenya. For all sets of parameters, boundaries of confidence domains were determined. Maximum calculated birth rates varied between 1.086 and 1.359 when empirical values were used for parameter estimation. After fitting of the models to the empirical trajectory, all birth rate values resulted considerably higher (1.742–3.526). The carrying capacity was determined between 13.0 and 39.9DBM/plant, after fitting of the models these values declined to 6.48–9.3, all values well within the range encountered empirically. The application of the Durbin–Watson criteria for comparison of theoretical and experimental population trajectories produced negative correlations with all models. A test of residual value groupings for randomness showed that their distribution is non-stochastic. In consequence, we conclude that DBM dynamics cannot be explained as a result of intra-population self-regulative mechanisms only (=by any of the models tested) and that more comprehensive models are required for the explanation of DBM population dynamics.
The BGO Calorimeter of BGO-OD Experiment Bantes, B; Bayadilov, D; Beck, R ...
Journal of physics. Conference series,
01/2015, Letnik:
587, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The BGO Rugby Ball is a large solid angle electromagnetic calorimeter now installed in the ELSA Facility in Bonn. The BGO is operating in the BGO-OD experiment aiming to study meson photoproduction ...off proton and neutron induced by a Bremsstrahlung polarized gamma beam of energies from 0.2 to 3.2 GeV and an intensity of 5 × 107 photons per second. The scintillating material characteristics and the photomultiplier read-out make this detector particularly suited for the detection of medium energy photons and electrons with very good energy resolution. The detector has been equipped with a new electronics read-out system, consisting of 30 sampling ADC Wie-Ne-R modules which perform the off-line reconstruction of the signal start-time allowing for a good timing resolution. Performances in linearity, resolution and time response have been carefully tested at the Beam Test Facility of the INFN National Laboratories in Frascati by using a matrix of 7 BGO crystals coupled to photomultipliers and equipped with the Wie-Ne-R sampling ADCs.
In current publication the statistical method of analysis of population time series in considered. This method is based on analysis of dynamics of non-linear ecological model parameter estimations in ...time, and devoted to investigation of influence of change of weather conditions on population dynamics (on the other words, it is devoted to analysis of climate change from the standpoint of separated population dynamics). Estimations of model parameters were obtained for parts (which contains 12 values each) of initial sample. For the approximation of sub-samples the well-known Kostitzin model of population size changing in time was used. It was used for the approximation of dataset of pine looper moth (Bupalus piniarius L.) dynamics in Germany (total sample size is 58). Estimation of model parameters were obtained with known least squares method. Analyses of tendencies of model parameter estimations showed that there are no reasons for rejecting hypotheses about the equalities of regression line angles to zero. It gives the base for conclusion about the absence of serious change in weather conditions in Germany during analyzing time interval (60 years).
Continuous-discrete model of population dynamics is considered in current publication. It is assumed that death process of individuals has a continuous nature, and appearences of individuals of new ...generations are observed at fixed time moments. It is also assumed that population has non-overlapping generations, and for every generation self-regulative mechanisms have distributed time lag in reaction on population size changing. For particular case when death rate of individuals between fixed time moments corresponds to Verhulst's law, it was obtained that various cyclic regimes can be observed in phase space. For various values of model parameters the structure of domain in space of parameters, where chaotic dynamic regimes can be realized, is described.
For the approximation of some of well-known time series of Paramecia aurelia and Paramecia caudatum (under the separated cultivation of both species) population size changing in time, some well-known ...models were used. For all considering models values of parameters were estimated with least square method (with global fitting) in two different ways: with and without additional limits for parameter values. In the case without additional limits for model parameters deviations between theoretical (model) trajectories and experimental time series were tested for Normality (Kolmogorov-Smirnov' test, and Shapiro-Wilk' test) with zero average, and for existence/absence of serial correlation (Durbin-Watson' criteria). The best results were observed for Gompertz' and Verhulst' models. Under the assumption that parameter K (maximum value of population size) is greater than all elements of initial sample the best results were observed for Gompertz model. In the last case the canonical technique for analysis of set of deviations can be applied in restricted form and needs in further development. In such a situation we cannot test the set of deviations on Normality with zero average (for big samples) because after a certain time moment all experimental points will be at one side of theoretical curve; at this situation we have to have a serial correlation in the sequence of deviations, etc.
BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be ...able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.
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