The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration...The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca（HzPO4）2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient （Kn） increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg（OH）z＇MgCIz＇8H20 in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.展开更多
In this paper, a sufficient condition for a balanced bipartite graph to contain a 2-factor F is given. We show that every balanced bipartite graph of order 2n (n≥6)and e(G)>n2−2n+4contains a 2-factor with k compon...In this paper, a sufficient condition for a balanced bipartite graph to contain a 2-factor F is given. We show that every balanced bipartite graph of order 2n (n≥6)and e(G)>n2−2n+4contains a 2-factor with k components, 2d1-cycle, ⋯, 2dk-cycle, if one of the following is satisfied: (1) k=2, δ(G)≥2and d1−2≥d2≥2;(2) k=3, δ(G)≥d3+2and d1−2≥d2≥d3≥4. In particular, this extends one result of Moon and Moser in 1963 under condition (1).展开更多
Liu and Yan gave the degree condition for a balanced bipartite graph G = （V1, V2; E） to have k vertex-disjoint quadrilaterals containing any given k independent edges e1,……, ek of G, respectively. They also conjec...Liu and Yan gave the degree condition for a balanced bipartite graph G = （V1, V2; E） to have k vertex-disjoint quadrilaterals containing any given k independent edges e1,……, ek of G, respectively. They also conjectured that for any k independent edges e1,……, ek of G, G has a 2-factor with k cycles C1, C2, ……, Ck with respect to {e1, e2,……, ek} such that k - 1 of them are quadrilaterals. In this paper, we prove this conjecture.展开更多
A path factor of G is a spanning subgraph of G such that its each component is a path.A path factor is called a P≥n-factor if its each component admits at least n vertices.A graph G is called P≥n-factor covered if G...A path factor of G is a spanning subgraph of G such that its each component is a path.A path factor is called a P≥n-factor if its each component admits at least n vertices.A graph G is called P≥n-factor covered if G admits a P≥n-factor containing e for any e∈E(G),which is defined by[Discrete Mathematics,309,2067-2076(2009)].We first define the concept of a(P≥n,k)-factor-critical covered graph,namely,a graph G is called(P≥n,k)-factor-critical covered if G-D is P≥n-factor covered for any D⊆V(G)with|D|=k.In this paper,we verify that(i)a graph G withκ(G)≥k+1 is(P≥2,k)-factor-critical covered if bind(G)>2+k/3;(ii)a graph G with|V(G)|≥k+3 andκ(G)≥k+1 is(P≥3,k)-factor-critical covered if bind(G)≥4+k/3.展开更多
基金Project(B0210)supported by One Hundred Talent Project of Chinese Academy of SciencesProject(2008-G-158)supported by Science and Technology Tackling Key Program of Qinghai Province,China
文摘The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca（HzPO4）2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient （Kn） increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg（OH）z＇MgCIz＇8H20 in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.
文摘In this paper, a sufficient condition for a balanced bipartite graph to contain a 2-factor F is given. We show that every balanced bipartite graph of order 2n (n≥6)and e(G)>n2−2n+4contains a 2-factor with k components, 2d1-cycle, ⋯, 2dk-cycle, if one of the following is satisfied: (1) k=2, δ(G)≥2and d1−2≥d2≥2;(2) k=3, δ(G)≥d3+2and d1−2≥d2≥d3≥4. In particular, this extends one result of Moon and Moser in 1963 under condition (1).
基金NNSF of China(10471078)Higher Education of MOE,P.R.C.(2004042204)
文摘Liu and Yan gave the degree condition for a balanced bipartite graph G = （V1, V2; E） to have k vertex-disjoint quadrilaterals containing any given k independent edges e1,……, ek of G, respectively. They also conjectured that for any k independent edges e1,……, ek of G, G has a 2-factor with k cycles C1, C2, ……, Ck with respect to {e1, e2,……, ek} such that k - 1 of them are quadrilaterals. In this paper, we prove this conjecture.
基金Supported by Six Big Talent Peak of Jiangsu Province(Grant No.JY–022)333 Project of Jiangsu Provincethe National Natural Science Foundation of China(Grant No.11371009)。
文摘A path factor of G is a spanning subgraph of G such that its each component is a path.A path factor is called a P≥n-factor if its each component admits at least n vertices.A graph G is called P≥n-factor covered if G admits a P≥n-factor containing e for any e∈E(G),which is defined by[Discrete Mathematics,309,2067-2076(2009)].We first define the concept of a(P≥n,k)-factor-critical covered graph,namely,a graph G is called(P≥n,k)-factor-critical covered if G-D is P≥n-factor covered for any D⊆V(G)with|D|=k.In this paper,we verify that(i)a graph G withκ(G)≥k+1 is(P≥2,k)-factor-critical covered if bind(G)>2+k/3;(ii)a graph G with|V(G)|≥k+3 andκ(G)≥k+1 is(P≥3,k)-factor-critical covered if bind(G)≥4+k/3.
