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21.
基于复杂性度量的心率变异信号非线性分析 总被引:2,自引:1,他引:1
假设心率变异信号是累积-发放模型(Integrate-fire)与非线性动力学系统耦合产生的峰电位链(SpikeTrain)。以符号动力学为基础,提出利用峰电位间隔(interspikeinterval,ISI)及其随机替代数据的C1、C2复杂度来定量刻划非线性动力学系统特性。结果表明:确定性驱动产生的峰电位间隔序列可以与随机性驱动产生的峰电位间隔序列区分开。因此,在噪声干扰较强的生理信号中,尤其是在不清楚非线性动力系统变量和峰电位间隔序列之间是否存在微分同胚的情况下,以复杂性度量来代替以Takens嵌入定理为基础的关联维数、Lyapnov指数等描述动力系统特征的方法是合适的。最后通过2类共37个个体,每个个体的心电数据为1000个R-R间期的微分序列检验心率变异信号的非线性结构。 相似文献
22.
We analyse spatial population dynamics showing that periodic or period-like chaotic dynamics produce self-organization structures, such as travelling waves. We suggest that self-organized patterns are associated with spatial synchrony patterns that often depend on geographical distance between subpopulations. The population dynamics also show statistical spatial autocorrelation patterns. We contrast our theoretical simulations with empirical data on annual damages in young sapling stands caused by voles. We conclude, on the basis of the periodicity, synchrony, and spatial autocorrelation patterns, and our simulation results, that vole dynamics represent travelling waves in population dynamics. We suggest that because such synchrony patterns are frequently observed in natural populations, spatial self-organization may be more common in population dynamics than reported in the literature. 相似文献
23.
It has been shown that, by adding a chaotic sequence to the weight update during the training of neural networks, the chaos injection-based gradient method (CIBGM) is superior to the standard backpropagation algorithm. This paper presents the theoretical convergence analysis of CIBGM for training feedforward neural networks. We consider both the case of batch learning as well as the case of online learning. Under mild conditions, we prove the weak convergence, i.e., the training error tends to a constant and the gradient of the error function tends to zero. Moreover, the strong convergence of CIBGM is also obtained with the help of an extra condition. The theoretical results are substantiated by a simulation example. 相似文献
24.
We show in this paper that the chaotic regimes of many food chain models often enjoy a very peculiar property, known as peak-to-peak dynamics. This means that the maximum (peak) density of the populations of any trophic level can be easily forecasted provided the last two peaks of the same population are known. Moreover, extensive simulation shows that only the last peak is needed if the forecast concerns the population at the top of the food chain and that peaks variability often increases from bottom to top. All these findings bring naturally to the conclusion that top populations should be sampled in order to have higher chances to detect peak-to-peak dynamics. The analysis is carried out by studying ditrophic food chain models with seasonally varying parameters, tritrophic food chain models with constant parameters, and more complex food chain and food web models. 相似文献
25.
26.
Jos M. Oliva-Lozano Víctor Fortes Jos M. Muyor 《Biology of sport / Institute of Sport》2021,38(2):165
The study aimed to compare the physical demands required during the first, second, and third most demanding passages (MDP) of play considering the effect of playing position, type of passage, and passage duration. A longitudinal study for three mesocycles was conducted in a professional soccer team competing in LaLiga123. Tracking systems collected total distance covered (DIS), high-speed running distance (HSRD), sprinting distance (SPD), total of high-intensity accelerations (ACCHIGH), and total of high-intensity decelerations (DECHIGH). The results confirmed that a significant effect of the type of passage (first, second or third MDP of play) on DIS (F(1.24, 178.89) = 115.53; p = 0.01; ηp2 = 0.45), HSRD (F(1.35, 195.36) = 422.82; p = 0.01; ηp2 = 0.75), SPD (F(1.43, 206.59) = 299.99; p = 0.01; ηp2 = 0.68), ACCHIGH (F(1.45, 209.38) = 268.59; p = 0.01; ηp2 = 0.65), and DECHIGH (F(1.45, 209.38) = 324.88; p = 0.01; ηp2 = 0.69) was found. In addition, a significant interaction between playing position, type and duration of the passage was observed in DIS (F(12.60, 453.47) = 1.98; p = 0.02; ηp2 = 0.05) and ACCHIGH (F(13.99, 503.78) = 1.92; p = 0.03; ηp2 = 0.06). In conclusion, significant differences in physical demands between the first, second, and third MDP of play were observed. However, there were some cases (DIS and ACCHIGH) in which no significant differences were found between these passages. Therefore, coaches should consider not only the magnitude of these peak intensity periods (e.g., distance covered per minute) but also the number of passages that players may experience during match play. 相似文献
27.
Because to defect is the evolutionary stable strategy in the prisoner’s dilemma game (PDG), understanding the mechanism generating
and maintaining cooperation in PDG, i.e. the paradox of cooperation, has intrinsic significance for understanding social altruism
behaviors. Spatial structure serves as the key to this dilemma. Here, we build the model of spatial PDG under a metapopulation
framework: the sub-populations of cooperators and defectors obey the rules in spatial PDG as well as the colonization–extinction
process of metapopulations. Using the mean-field approximation and the pair approximation, we obtain the differential equations
for the dynamics of occupancy and spatial correlation. Cellular automaton is also built to simulate the spatiotemporal dynamics
of the spatial PDG in metapopulations. Join-count statistics are used to measure the spatial correlation as well as the spatial
association of the metapopulation. Simulation results show that the distribution is self-organized and that it converges to
a static boundary due to the boycotting of cooperators to defectors. Metapopulations can survive even when the colonization
rate is lower than the extinction rate due to the compensation of cooperation rewards for extinction debt. With a change of
parameters in the model, a metapopulation can consist of pure cooperators, pure defectors, or cooperator–defector coexistence.
The necessary condition of cooperation evolution is the local colonization of a metapopulation. The spatial correlation between
the cooperators tends to be weaker with the increase in the temptation to defect and the habitat connectivity; yet the spatial
correlation between defectors becomes stronger. The relationship between spatial structure and the colonization rate is complicated,
especially for cooperators. The metapopulation may undergo a temporary period of prosperity just before the extinction, even
while the colonization rate is declining.
An erratum to this article can be found at 相似文献
28.
Here we extend the classic Hawk-Dove model of animal conflict to allow for continuous variation in fighting strengths. Whereas the winner of a fight is chosen at random in the discrete game, in our continuous game, the winner of any fight is the stronger individual, and costs are higher for more evenly matched opponents. We identify the evolutionary stable strength threshold beyond which an animal should be prepared to engage in aggressive behaviour and show that this threshold increases with variance in fighting strength when the costs of aggression are insensitive to the level of strength asymmetry, but decreases with variance when the costs are sensitive to the level of asymmetry. In contrast to the classic discrete game, population-wide aggressive behaviour occurs only when the costs of fighting are zero. It is now known that animals can eavesdrop on the outcome of contests between neighbours and modify their behaviour towards observed winners and losers. We therefore further extend our model to allow for social eavesdropping within networks comprising three individuals. Whereas earlier work showed that eavesdropping increases the frequency of mutually aggressive contests in the discrete game by enhancing the value of victory, here we show that aggression thresholds in the continuous game are always higher with eavesdropping than without it: for sufficiently weak animals, avoiding the costs of challenging an observed winner over-rides the potential benefit of winning, so that eavesdropping reduces the frequency of aggressive encounters. Thus, even though strength is not directly observable, information is extracted from the variation in fighting ability that the classic Hawk-Dove game ignores. 相似文献
29.
RODNEY D. BOERTJE KALIN A. KELLIE C. TOM SEATON MARK A. KEECH DONALD D. YOUNG BRUCE W. DALE LAYNE G. ADAMS ANDREW R. ADERMAN 《The Journal of wildlife management》2007,71(5):1494-1506
Abstract: We focused on describing low nutritional status in an increasing moose (Alces alces gigas) population with reduced predation in Game Management Unit (GMU) 20A near Fairbanks, Alaska, USA. A skeptical public disallowed liberal antlerless harvests of this moose population until we provided convincing data on low nutritional status. We ranked nutritional status in 15 Alaska moose populations (in boreal forests and coastal tundra) based on multiyear twinning rates. Data on age-of-first-reproduction and parturition rates provided a ranking consistent with twinning rates in the 6 areas where comparative data were available. Also, short-yearling mass provided a ranking consistent with twinning rates in 5 of the 6 areas where data were available. Data from 5 areas implied an inverse relationship between twinning rate and browse removal rate. Only in GMU 20A did nutritional indices reach low levels where justification for halting population growth was apparent, which supports prior findings that nutrition is a minor factor limiting most Alaska moose populations compared to predation. With predator reductions, the GMU 20A moose population increased from 1976 until liberal antlerless harvests in 2004. During 1997-2005, GMU 20A moose exhibited the lowest nutritional status reported to date for wild, noninsular, North American populations, including 1) delayed reproduction until moose reached 36 months of age and the lowest parturition rate among 36-month-old moose (29%, n = 147); 2) the lowest average multiyear twinning rates from late-May aerial surveys (x = 7%, SE = 0.9%, n = 9 yr, range = 3-10%) and delayed twinning until moose reached 60 months of age; 3) the lowest average mass of female short-yearlings in Alaska (x̄ = 155 ± 1.6 [SE] kg in the Tanana Flats subpopulation, up to 58 kg below average masses found elsewhere); and 4) high removal (42%) of current annual browse biomass compared to 9-26% elsewhere in boreal forests. When average multiyear twinning rates in GMU 20A (sampled during 1960-2005) declined to <10% in the mid- to late 1990s, we began encouraging liberal antlerless harvests, but only conservative annual harvests of 61-76 antlerless moose were achieved during 1996-2001. Using data in the context of our broader ranking system, we convinced skeptical citizen advisory committees to allow liberal antlerless harvests of 600-690 moose in 2004 and 2005, with the objective of halting population growth of the 16,000-17,000 moose; total harvests were 7-8% of total prehunt numbers. The resulting liberal antlerless harvests served to protect the moose population's health and habitat and to fulfill a mandate for elevated yield. Liberal antlerless harvests appear justified to halt population growth when multiyear twinning rates average ≤10% and ≥1 of the following signals substantiate low nutritional status: <50% of 36-month-old moose are parturient, average multiyear short-yearling mass is <175 kg, or >35% of annual browse biomass is removed by moose. 相似文献
30.
Robert R. Jackson Mark W. Walker Simon D. Pollard Fiona R. Cross 《Journal of Ethology》2006,24(3):231-238
An important prediction from game theory is that resource value influences the level to which competitors will escalate conflict. An earlier study considered whether this prediction applies to the male–male interactions of Hypoblemum albovittatum, a jumping spider (Salticidae) from New Zealand. The males of this species escalated conflicts in the presence of a moving mount made from a conspecific female. However, because the control was only a similar-sized motionless cork, an alternative hypothesis (that the cue for escalation is seeing movement of any female-size object, rather than seeing specifically a female) was not ruled out. Here we show that a moving cork, without a mount present, is indeed sufficient to cause males to escalate, but a moving mount (made from a conspecific female) causes males to escalate further. The level of escalation in the presence of a moving mount made from prey (housefly) or from a rival (conspecific male) did not differ significantly from the level of escalation when only a moving cork was present. These findings suggest that, although seeing a moving object similar in size to a conspecific female is sufficient for priming males to escalate, males can also discern by sight that specifically a female is present and, when they have this precise information, they make strategic decisions to escalate conflict further. 相似文献