Changping Wang

Learn More
We present a deterministic model for on-line social networks based on transitivity and local knowledge in social interactions. In the Iterated Local Transitivity (ILT) model, at each time-step and for every existing node x, a new node appears which joins to the closed neighbour set of x. The ILT model provably satisfies a number of both local and global(More)
A bad function is a function f : V (G) → {−1, 1} satisfying ∑ v∈N(v) f(v) ≤ 1 for every v ∈ V (G), where N(v) = {u ∈ V (G) | uv ∈ E(G)}. The maximum of the values of ∑ v∈V (G) f(v), taken over all bad functions f, is called the negative decision number and is denoted by βD(G). In this paper, several sharp upper bounds of this number for general graphs are(More)
We consider the game of Cops and Robber played with infinitely many cops on countable graphs. We give a sufficient condition— the strongly 1-e.c. property—for the cop number to be infinite. The cop density of a finite graph, defined as the ratio of the cop number and the number of vertices, is investigated. In the infinite case, the limits of the cop(More)
In this work, the authors consider the fourth order nonlinear ordinary differential equation u(4)(t) = f (t, u(t)), 0 < t < 1, with the four-point boundary conditions u(0) = u(1) = 0, au′′(ξ1)− bu′′′(ξ1) = 0, cu′′(ξ2)+ du′′′(ξ2) = 0, where 0 ≤ ξ1 < ξ2 ≤ 1. By means of the upper and lower solution method and fixed point theorems, some results on the(More)
We present a deterministic model for on-line social networks (OSNs) based on transitivity and local knowledge in social interactions. In the Iterated Local Transitivity (ILT) model, at each time-step and for every existing node x, a new node appears which joins to the closed neighbour set of x. The ILT model provably satisfies a number of both local and(More)
In this Letter, an approach of adaptive synchronization and parameters identification of uncertain Rössler hyperchaotic system is proposed. The suggested tool proves to be globally and asymptotically stable by means of Lyapunov method. With this new and effective method, parameters identification and synchronization of Rössler hyperchaotic with all the(More)
Vertex pursuit games, such as the game of Cops and Robbers, are a simplified model for network security. In these games, cops try to capture a robber loose on the vertices of the network. The minimum number of cops required to win on a graph G is the cop number of G. We present asymptotic results for the game of Cops and Robbers played in various stochastic(More)
For any integer k ≥ 1, a signed (total) k-dominating function is a function f : V (G) → {−1, 1} satisfying w∈N [v] f(w) ≥ k ( P w∈N(v) f(w) ≥ k) for every v ∈ V (G), where N(v) = {u ∈ V (G)|uv ∈ E(G)} and N [v] = N(v)∪{v}. The minimum of the values ofv∈V (G) f(v), taken over all signed (total) k-dominating functions f, is called the signed (total)(More)