光皮桦林优势树种间的竞争

研究了福建省卫闽光皮桦林内优势树种间的竞争关系,结果表明：光皮桦与锥栗、枫香、拟赤杨间的竞争较为激烈,并且光皮桦与锥栗、光皮桦与丝栗栲之间达到了暂时相对稳定的平衡。另外,光皮桦在与其它主要伴生树种的竞争中,目前处于优势地位。     

青海高校男子篮球运动员竞技水平现状分析与研究

通过对青海省大学生男子篮球主要赛事的临场观察与技术统计,在此基础上进行分析与研究,目的在于深刻认识目前青海省高校男子篮球竞技水平的现状.找出存在的问题,为提高青海高校男篮竞技水平提供一些理论依据,研究结果表明:目前青海高校男子篮球竞技水平总体较低,技战术运用不合理,竞技能力不够,暂不具备与较高水平的大学生队竞赛抗衡的能力.     

Dynamical behaviors of a classical Lotka–Volterra competition–diffusion–advection system

This paper deals with a two-species competition model in a homogeneous advective environment, where two species are subjected to a net loss of individuals at the downstream end. Under the assumption that the advection and diffusion rates of two species are proportional, we give a basic classification on the global dynamics by employing the theory of monotone dynamical system. It turns out that bistability does not happen, but coexistence and competitive exclusion may occur. Furthermore, we present a complete classification on the global dynamics in terms of the growth rates of two species. However, once the above assumption does not hold, bistability may occur. In detail, there exists a tradeoff between growth rates of two species such that competition outcomes can shift between three possible scenarios, including competitive exclusion, bistability and coexistence. These results show that growth competence is important to determine dynamical behaviors.     

The competition number of a graph and the dimension of its hole space

The competition graph of a digraph D is a (simple undirected) graph which has the same vertex set as D and has an edge between x and y if and only if there exists a vertex v in D such that (x,v) and (y,v) are arcs of D. For any graph G, G together with sufficiently many isolated vertices is the competition graph of some acyclic digraph. The competition number k(G) of G is the smallest number of such isolated vertices. In general, it is hard to compute the competition number k(G) for a graph G and it has been one of the important research problems in the study of competition graphs to characterize a graph by its competition number. Recently, the relationship between the competition number and the number of holes of a graph has been studied. A hole of a graph is a cycle of length at least 4 as an induced subgraph. In this paper, we conjecture that the dimension of the hole space of a graph is not smaller than the competition number of the graph. We verify this conjecture for various kinds of graphs and show that our conjectured inequality is indeed an equality for connected triangle-free graphs.     

Competition of three species in an advective environment

Individuals in advective environments, for example rivers, coastlines, or the gut, are subject to movement with directional bias. We study how this movement bias shapes community composition by considering how the strength of movement bias affects the outcome of competition among three species. Our model is a system of three reaction-advection-diffusion equations with Danckwerts boundary conditions. Our key tool in this study is to use the dominant eigenvalue of the diffusion-advection operator in order to reduce the spatially explicit model to a spatially implicit ordinary differential equation model. After an in-depth analysis of the implicit model, we use numerical simulations of the explicit model to test the predictions obtained from the analysis. In general, we find a good qualitative agreement between the explicit and the implicit model. We find that varying the strength of advection can fundamentally alter the outcome of competition between the three species, and we characterize the possible transitions. In particular, water extraction and flow control can destabilize existing species communities or facilitate invasions of non-native species.     

Evolutionary model of the personal income distribution

The aim of this work is to develop a qualitative picture of the personal income distribution. Treating an economy as a self-organized system the key idea of the model is that the income distribution contains competitive and non-competitive contributions. The presented model distinguishes between three main income classes. 1. Capital income from private firms is shown to be the result of an evolutionary competition between products. A direct consequence of this competition is Gibrat’s law suggesting a lognormal income distribution for small private firms. Taking into account an additional preferential attachment mechanism for large private firms the income distribution is supplemented by a power law (Pareto) tail. 2. Due to the division of labor a diversified labor market is seen as a non-competitive market. In this case wage income exhibits an exponential distribution. 3. Also included is income from a social insurance system. It can be approximated by a Gaussian peak. A consequence of this theory is that for short time intervals a fixed ratio of total labor (total capital) to net income exists (Cobb–Douglas relation). A comparison with empirical high resolution income data confirms this pattern of the total income distribution. The theory suggests that competition is the ultimate origin of the uneven income distribution.     

Discrete May–Leonard Competition Models III

A discretization method attributed to Kahan is used to approximate the May–Leonard (M–L) competition model for three species. The local dynamics of this discrete-time M–L model are analyzed. This model differs from the discrete M–L models being studied previously. This discrete model shows dynamical consistency with the continuous M–L model. Numerically, we showed that the discrete M–L model has a degenerate Hopf-bifurcation, which is consistent with the continuous M–L model.     

简化分类相关器模型——DCR模型

本文提出一个DCR模型——以深度结构DA、竞争结构CA和相关联想结构RA为一体的模型,通过DA进行输入向量的特征集分类,再通过CA竞争出最重要特征,再由RA找到与之关系最紧密的特征表达,并进行相应的回忆,从而实现重要特征的提取和联想,并作为系统输出或控制结构的决策参数。     

Continuous time random walk with jump length correlated with waiting time

A coupled continuous time random walk (CTRW) model is proposed, in which the jump length of a walker is correlated with waiting time. The power law distribution is chosen as the probability density function of waiting time and the Gaussian-like distribution as the probability density function of jump length. Normal diffusion, subdiffusion and superdiffusion can be realized within the present model. It is shown that the competition between long-tailed distribution and correlation of jump length and waiting time will lead to different diffusive behavior.