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Weak solutions to a nonlinear variational wave equation and some related problems

Ping Zhang — 2006

Applications of Mathematics

In this paper we present some results on the global existence of weak solutions to a nonlinear variational wave equation and some related problems. We first introduce the main tools, the L p Young measure theory and related compactness results, in the first section. Then we use the L p Young measure theory to prove the global existence of dissipative weak solutions to the asymptotic equation of the nonlinear wave equation, and comment on its relation to Camassa-Holm equations in the second section....

On k -strong distance in strong digraphs

Ping Zhang — 2002

Mathematica Bohemica

For a nonempty set S of vertices in a strong digraph D , the strong distance d ( S ) is the minimum size of a strong subdigraph of D containing the vertices of S . If S contains k vertices, then d ( S ) is referred to as the k -strong distance of S . For an integer k 2 and a vertex v of a strong digraph D , the k -strong eccentricity s e k ( v ) of v is the maximum k -strong distance d ( S ) among all sets S of k vertices in D containing v . The minimum k -strong eccentricity among the vertices of D is its k -strong radius s r a d k D and the maximum...

On k-Path Pancyclic Graphs

Zhenming BiPing Zhang — 2015

Discussiones Mathematicae Graph Theory

For integers k and n with 2 ≤ k ≤ n − 1, a graph G of order n is k-path pancyclic if every path P of order k in G lies on a cycle of every length from k + 1 to n. Thus a 2-path pancyclic graph is edge-pancyclic. In this paper, we present sufficient conditions for graphs to be k-path pancyclic. For a graph G of order n ≥ 3, we establish sharp lower bounds in terms of n and k for (a) the minimum degree of G, (b) the minimum degree-sum of nonadjacent vertices of G and (c) the size of G such that G...

On Closed Modular Colorings of Trees

Bryan PhinezyPing Zhang — 2013

Discussiones Mathematicae Graph Theory

Two vertices u and v in a nontrivial connected graph G are twins if u and v have the same neighbors in V (G) − {u, v}. If u and v are adjacent, they are referred to as true twins; while if u and v are nonadjacent, they are false twins. For a positive integer k, let c : V (G) → Zk be a vertex coloring where adjacent vertices may be assigned the same color. The coloring c induces another vertex coloring c′ : V (G) → Zk defined by c′(v) = P u∈N[v] c(u) for each v ∈ V (G), where N[v] is the closed neighborhood...

On graphs with a unique minimum hull set

Gary ChartrandPing Zhang — 2001

Discussiones Mathematicae Graph Theory

We show that for every integer k ≥ 2 and every k graphs G₁,G₂,...,Gₖ, there exists a hull graph with k hull vertices v₁,v₂,...,vₖ such that link L ( v i ) = G i for 1 ≤ i ≤ k. Moreover, every pair a, b of integers with 2 ≤ a ≤ b is realizable as the hull number and geodetic number (or upper geodetic number) of a hull graph. We also show that every pair a,b of integers with a ≥ 2 and b ≥ 0 is realizable as the hull number and forcing geodetic number of a hull graph.

The forcing geodetic number of a graph

Gary ChartrandPing Zhang — 1999

Discussiones Mathematicae Graph Theory

For two vertices u and v of a graph G, the set I(u, v) consists of all vertices lying on some u-v geodesic in G. If S is a set of vertices of G, then I(S) is the union of all sets I(u,v) for u, v ∈ S. A set S is a geodetic set if I(S) = V(G). A minimum geodetic set is a geodetic set of minimum cardinality and this cardinality is the geodetic number g(G). A subset T of a minimum geodetic set S is called a forcing subset for S if S is the unique minimum geodetic set containing T. The forcing geodetic...

On stratification and domination in graphs

Ralucca GeraPing Zhang — 2006

Discussiones Mathematicae Graph Theory

A graph G is 2-stratified if its vertex set is partitioned into two classes (each of which is a stratum or a color class), where the vertices in one class are colored red and those in the other class are colored blue. Let F be a 2-stratified graph rooted at some blue vertex v. An F-coloring of a graph is a red-blue coloring of the vertices of G in which every blue vertex v belongs to a copy of F rooted at v. The F-domination number γ F ( G ) is the minimum number of red vertices in an F-coloring of G. In...

Connected partition dimensions of graphs

Varaporn SaenpholphatPing Zhang — 2002

Discussiones Mathematicae Graph Theory

For a vertex v of a connected graph G and a subset S of V(G), the distance between v and S is d(v,S) = mind(v,x)|x ∈ S. For an ordered k-partition Π = S₁,S₂,...,Sₖ of V(G), the representation of v with respect to Π is the k-vector r(v|Π) = (d(v,S₁), d(v,S₂),..., d(v,Sₖ)). The k-partition Π is a resolving partition if the k-vectors r(v|Π), v ∈ V(G), are distinct. The minimum k for which there is a resolving k-partition of V(G) is the partition dimension pd(G) of G. A resolving partition Π = S₁,S₂,...,Sₖ...

Nowhere-zero modular edge-graceful graphs

Ryan JonesPing Zhang — 2012

Discussiones Mathematicae Graph Theory

For a connected graph G of order n ≥ 3, let f: E(G) → ℤₙ be an edge labeling of G. The vertex labeling f’: V(G) → ℤₙ induced by f is defined as f ' ( u ) = v N ( u ) f ( u v ) , where the sum is computed in ℤₙ. If f’ is one-to-one, then f is called a modular edge-graceful labeling and G is a modular edge-graceful graph. A modular edge-graceful labeling f of G is nowhere-zero if f(e) ≠ 0 for all e ∈ E(G) and in this case, G is a nowhere-zero modular edge-graceful graph. It is shown that a connected graph G of order n ≥ 3 is nowhere-zero...

Semiclassical Limit of the cubic nonlinear Schrödinger Equation concerning a superfluid passing an obstacle

Fanghua LinPing Zhang

Séminaire Équations aux dérivées partielles

In this paper, we study the semiclassical limit of the cubic nonlinear Schrödinger equation with the Neumann boundary condition in an exterior domain. We prove that before the formation of singularities in the limit system, the quantum density and the quantum momentum converge to the unique solution of the compressible Euler equation with the slip boundary condition as the scaling parameter approaches 0 .

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