网络结构和信息披露对网络参与主体的收益影响研究

网络结构和网络上的信息披露机制对网络功能的发挥有着直接的影响,建立相应的数学模型并采用数学分析和仿真验证的手段揭示其对于网络参与主体收益的影响规律,具有理论和应用价值。在明确网络中两类参与主体的基础上,定义了他们的收益,并根据信息披露的不同情形,分为两种情况求解模型,应用数学证明和仿真分析的手段得到了网络结构对收益影响规律的三个结论。在对结论分析的基础上,指出了模型的管理学意义,讨论了进一步的研究工作。     

ENVIRONMENTAL CHANGE AND THE CONTRIBUTION OF BIODIVERSITY TO ECOSYSTEM ADAPTATION

Abstract This paper develops a measure of the contribution of biodiversity in enhancing ecosystem performance that is subject to environmental fluctuation. The analysis draws from an ecological model that relates high phenotypic variance with lower short‐term productivity (due to the presence of suboptimal species) and higher long‐term productivity (due to better ability to respond to environmental fluctuations). This feature, which is a notable extension to existing economic‐ecological models of biodiversity, enables assessment of the interactions between diversity and a range of environmental fluctuations to highlight that biodiversity could be rendered economically disadvantageous when environmental fluctuation is insufficient. The resulting economic‐ecological model generates discounted present value of harvests for an ecosystem with diverse set of species. This value is compared with the harvest value of a similar economic‐ecological model with no diversity and that of an ecosystem where the dynamics of phenotypes in response to environmental fluctuations is disregarded. The results show that diversity positively contributes to the performance of ecosystems subject to sufficiently large environmental fluctuation. In addition, neglecting an ecosystem's increasing ability to adapt to match environmental conditions is also shown to be more costly than having no diversity in an otherwise identical ecosystem.     

Fitness model for tiered structure in the interbank market

Tiered structure is observed in a range of countries' banking systems. In that case, relatively few first‐tier banks are not only interconnected, but are connected with second‐tier banks, whereas second‐tier banks are almost exclusively connected with first‐tier banks. This study uses the theory of complex networks to quantitatively characterize the formation of tiered structure in banking systems. The interbank market network model constructed in this article reproduces tiered structure and various statistical properties, namely, a small‐world property and a disassortative mixing property as well as a reciprocal property. This network modeling of the interbank market could be an efficient way to understand the bank behavior in the interbank market. © 2012 Wiley Periodicals, Inc. Complexity, 2012     

完全k叉树的粘连度

相对于其他网络抗毁性的描述指标来说,图的粘连度是比较理想,也是比较合理的刻画参数．而完全k叉树作为重要的网络结构被广泛地应用在通信网和嵌入式系统芯片的优化设计方面．本文通过优化组合方法界定了完全k叉树的粘连度和毁裂度．从某种程度刻画了网络的抗毁性,为网络设计提供了一种客观的理论依据．完全k叉树的粘连度为1k＋1（kh＋1-1）,如h是奇数;1k＋1（（kh＋1-1）,如h是偶数．完全k叉树的毁裂度为（2k-1）kh-12,如h是奇数;kh＋22-1k-1,如h是偶数．     

Optimal algorithms for computing edge weights in planar split networks

In phylogenetics, biologists commonly compute split networks when trying to better understand evolutionary data. These graph-theoretical structures represent collections of weighted bipartitions or splits of a finite set, and provide a means to display conflicting evolutionary signals. The weights associated to the splits are used to scale the edges in the network and are often computed using some distance matrix associated with the data. In this paper we present optimal polynomial time algorithms for three basic problems that arise in this context when computing split weights for planar split-networks. These generalize algorithms that have been developed for special classes of split networks (namely, trees and outer-labeled planar networks). As part of our analysis, we also derive a Crofton formula for full flat split systems, structures that naturally arise when constructing planar split-networks.     

CANADA'S FOREST COVER INDICATOR: DEFINITION,METHODOLOGY AND RESULTS

ABSTRACT. The Environment and Sustainable Development Indicators (ESDI) Initiative was introduced to track Canada's overall wealth in the form of natural and human capital, in additionto familiar economic data such as the gross domestic product (GDP). One of the six ESDIs is the Forest Cover Indicator (FCI). In this paper we define FCI, outline the overall method for deriving FCI, and report results for addressing four key technical issues in carrying out this overall method. The FCI is defined as interannual variations of Canada's forest area with the middle‐summer crown closure (CC) ? 10%. Crown closure is the percentage of the ground surface covered by a downward vertical projection of the tree crowns. Theoverall monitoring method is mainly based on coarse resolution remote sensing data because of the need to cover Canada's extensive landmass during the middle‐summer months and toupdate the results annually. Medium resolution satellite data, field measurements, and modeling approaches were used for calibration, correction, validation, and down‐scaling, with a focus on the following 4 key technical issues: (1) correcting understory non‐tree vegetation effect on CC, (2) downscaling forest cover area from 1‐km to 100‐m spatial resolution as required by the FCI definition, (3) detecting the changes of CC caused by disturbances, and (4) detecting changes in CC caused by forest regrowth. Methods and results for addressing these technical issues are described in the paper. While these results indicate that the key technical issues can be solved by integrating satellite remote sensing data/products and other data, there are clear needs for further development, especially testing against field measurements.     

The cut‐tree of large trees with small heights

We destroy a finite tree of size n by cutting its edges one after the other and in uniform random order. Informally, the associated cut‐tree describes the genealogy of the connected components created by this destruction process. We provide a general criterion for the convergence of the rescaled cut‐tree in the Gromov‐Prohorov topology to an interval endowed with the Euclidean distance and a certain probability measure, when the underlying tree has branching points close to the root and height of order . In particular, we consider uniform random recursive trees, binary search trees, scale‐free random trees and a mixture of regular trees. This yields extensions of a result in Bertoin (Probab Stat 5 (2015), 478–488) for the cut‐tree of uniform random recursive trees and also allows us to generalize some results of Kuba and Panholzer (Online J Anal Combin (2014), 26) on the multiple isolation of vertices. The approach relies in the close relationship between the destruction process and Bernoulli bond percolation, which may be useful for studying the cut‐tree of other classes of trees. © 2017 Wiley Periodicals, Inc. Random Struct. Alg., 51, 404–427, 2017     

The Height of Increasing Trees

Increasing trees have been introduced by Bergeron, Flajolet, and Salvy [1]. This kind of notion covers several well-know classes of random trees like binary search trees, recursive trees, and plane oriented (or heap ordered) trees. We consider the height of increasing trees and prove for several classes of trees (including the above mentioned ones) that the height satisfies EH _n ~ γlogn (for some constant γ > 0) and Var H _n =  O(1) as n → ∞. The methods used are based on generating functions. This research was supported by the Austrian Science Foundation FWF, project S9604, that is part of the Austrian National Research Network "Analytic Combinatorics and Probabilistic Number Theory".     

Stochastic Enumeration Method for Counting Trees

The problem of estimating the size of a backtrack tree is an important but hard problem in the computational sciences. An efficient solution of this problem can have a major impact on the hierarchy of complexity classes. The first randomized procedure, which repeatedly generates random paths through the tree, was introduced by Knuth. Unfortunately, as was noted by Knuth and a few other researchers, the estimator can introduce a large variance and become ineffective in the sense that it underestimates the cost of the tree. Recently, a new sequential algorithm called Stochastic Enumeration (SE) method was proposed by Rubinstein et al. The authors showed numerically that this simple algorithm can be very efficient for handling different counting problems, such as counting the number of satisfiability assignments and enumerating the number of perfect matchings in bipartite graphs. In this paper we introduce a rigorous analysis of SE and show that it results in significant variance reduction as compared to Knuth’s estimator. Moreover, we establish that for almost all random trees the SE algorithm is a fully polynomial time randomized approximation scheme (FPRAS) for the estimation of the overall tree size.     

结构开放式神经网络及其应用

将传统模式识别神经网络与人类认知的方式相结合,提出了结构开放式模式识别神经网络的概念,并设计了结构开放式模式识别神经网络的体系结构.与传统模式识别神经网络相比,这种神经网络不但提高了神经网络的学习记忆功能,而且在利用计算机实现智能化时大大减少了数据结构的数据量.为了能够更容易的理解这种网络,并针对一类特殊情况的应用进行研究,设计了一个结构开放式模式识别神经网络的结构和操作流程,并通仿真试验,证明了这种网络的有效性和实用性.     

Detecting evolving patterns of self‐organizing networks by flow hierarchy measurement

Hierarchies occur widely in evolving self‐organizing ecological, biological, technological, and social networks, but detecting and comparing hierarchies is difficult. Here we present a metric and technique to quantitatively assess the extent to which self‐organizing directed networks exhibit a flow hierarchy. Flow hierarchy is a commonly observed but theoretically overlooked form of hierarchy in networks. We show that the ecological, neurobiological, economic, and information processing networks are generally more hierarchical than their comparable random networks. We further discovered that hierarchy degree has increased over the course of the evolution of Linux kernels. Taken together, our results suggest that hierarchy is a central organizing feature of real‐world evolving networks, and the measurement of hierarchy opens the way to understand the structural regimes and evolutionary patterns of self‐organizing networks. Our measurement technique makes it possible to objectively compare hierarchies of different networks and of different evolutionary stages of a single network, and compare evolving patterns of different networks. It can be applied to various complex systems, which can be represented as directed networks. © 2011 Wiley Periodicals, Inc. Complexity, 2011     

Some Spreading Properties of a Monotone Non-autonomous Parabolic Equation in a Periodic Cylinder

In our study of electrical networks we develop two themes: finding explicit formulas for special classes of functions defined on the vertices of a transient network, namely monopoles, dipoles, and harmonic functions. Secondly, our interest is focused on the properties of electrical networks supported on Bratteli diagrams. We show that the structure of Bratteli diagrams allows one to describe algorithmically harmonic functions as well as monopoles and dipoles. We also discuss some special classes of Bratteli diagrams (stationary, Pascal, trees), and we give conditions under which the harmonic functions defined on these diagrams have finite energy.

     

Simulation study of dissimilarity between point process

The spatial distributions of two species of tree result in a bivariate pattern. This pattern characterizes biological mechanism involved within a forest with the spatial localization of the trees. If we consider simultaneously two species, the main question is not to describe the marginal distribution of each species but to describe the relationship between the repartitions of the two species under study. The relationship between two clouds of points can be described in various ways and therefore many indices can be defined. Each index will give a specific information about these relationships and will greatly depends on the ecological mechanisms, i.e., the point process that leads to the observed repartition. The aim of this article is to review the leading indices in ecology and to provide guidelines for practical use. To mimic ecological situations, we simulated 13 point process that can model classical relationships between two species of trees and compute nine classical indices. The interest of the various indices are discussed. A R package for simulating the point process and to compute the indices is available on request. The package is available upon request at picard@cirad.fr or avner@inapg.fr     

Protected Branches in Ordered Trees

In this paper, we consider the class of ordered trees and its two subclasses, bushes and planted trees, which consist of the ordered trees with root degree at least $2$ and with root degree $1$ respectively. In these three classes, we study the number of trees of size $n$ with $k$ protected (resp. unprotected) branches, and the total number of branches (resp. protected branches, unprotected branches) among all trees of size $n$. The explicit formulas as well as the generating functions are obtained. Furthermore, we find that, in each class, as $n$ goes to infinity, the proportion of protected branches among all branches in all trees of size $n$ approaches $ 1/3$.     

Structure and rigidity in hyperbolic groups I

We introduce certain classes of hyperbolic groups according to their possible actions on real trees. Using these classes and results from the theory of (small) group actions on real trees, we study the structure of hyperbolic groups and their automorphism group.The second author was partially supported by an NSF grant.     

ARTIFICIAL NEURAL NETWORK MODELING FOR REFORESTATION DESIGN THROUGH THE DOMINANT TREES BOLE‐VOLUME ESTIMATION

Abstract In the management of restoration reforestations or recreational reforestations of trees, the density of the planted trees and the site conditions can influence the growth and bole volume of the dominant tree. The ability to influence growth of these trees in a reforestation contributes greatly to the formation of large dimension trees and thereby to the production of commercially valuable wood. The potential of two artificial neural network (ANN) architectures in modeling the dominant Pinus brutia tree bole volume in reforestation configuration at 12 years of age was investigated: (1) the multilayer perceptron architecture using a back‐propagation algorithm and (2) the cascade‐correlation architecture, utilizing (a) either the nonlinear Kalman's filter theory or (b) the adaptive gradient descent learning rule. The incentive for developing bole‐volume equations using ANN techniques was to demonstrate an alternative new methodology in the field of reforestation design, which would enable estimation and optimization of the bole volume of dominant trees in reforestations using easily measurable site and competition factors. The usage of the ANNs for the estimation of dominant tree bole volume through site and competition factors can be a very useful tool in forest management practice.     

A review of urban transportation network design problems

This paper presents a comprehensive review of the definitions, classifications, objectives, constraints, network topology decision variables, and solution methods of the Urban Transportation Network Design Problem (UTNDP), which includes both the Road Network Design Problem (RNDP) and the Public Transit Network Design Problem (PTNDP). The current trends and gaps in each class of the problem are discussed and future directions in terms of both modeling and solution approaches are given. This review intends to provide a bigger picture of transportation network design problems, allow comparisons of formulation approaches and solution methods of different problems in various classes of UTNDP, and encourage cross-fertilization between the RNDP and PTNDP research.     

基于二次优化BP神经网络的期货价格预测

针对BP算法存在的不足,结合神经网络、遗传算法和主成分分析的优点,提出基于二次优化BP神经网络的期货价格预测算法.初次优化采用主成分分析法对网络结构进行优化,第二次优化采用自适应遗传算法对网络参数进行优化,将经过二次优化后建立的BP神经网络模型用于期货价格预测.经仿真检验,用新方法建立的模型对期货价格进行预测,在预测的精度和速度方面都优于单纯BP神经网络模型.     

The distribution of height and diameter in random non‐plane binary trees

This study is dedicated to precise distributional analyses of the height of non‐plane unlabelled binary trees (“Otter trees”), when trees of a given size are taken with equal likelihood. The height of a rooted tree of size n is proved to admit a limiting theta distribution, both in a central and local sense, and obey moderate as well as large deviations estimates. The approximations obtained for height also yield the limiting distribution of the diameter of unrooted trees. The proofs rely on a precise analysis, in the complex plane and near singularities, of generating functions associated with trees of bounded height. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2012