We show that for every rational number r∈(1,2)of the form 2-a/b,where a,b∈N^(+)satisfy[b/a]^(3)≤a≤b/([b/a]+1)+1,there exists a graph Frsuch that the Turán number ex(n,F_(r))=Θ(n^(r)).Our result in particular...We show that for every rational number r∈(1,2)of the form 2-a/b,where a,b∈N^(+)satisfy[b/a]^(3)≤a≤b/([b/a]+1)+1,there exists a graph Frsuch that the Turán number ex(n,F_(r))=Θ(n^(r)).Our result in particular generates infinitely many new Turán exponents.As a byproduct,we formulate a framework that is taking shape in recent work on the Bukh–Conlon conjecture.展开更多
The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant...The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.展开更多
基金supported in part by U.S.taxpayers through the National Science Foundation(NSF)grant DMS-1855542by U.S.taxpayers through NSF grant DMS-1953946+3 种基金supported in part by an AMS Simons Travel Grantsupported in part by the National Key R&D Program of China 2020YFA0713100National Natural Science Foundation of China grants 11622110 and 12125106Anhui Initiative in Quantum Information Technologies grant AHY150200。
文摘We show that for every rational number r∈(1,2)of the form 2-a/b,where a,b∈N^(+)satisfy[b/a]^(3)≤a≤b/([b/a]+1)+1,there exists a graph Frsuch that the Turán number ex(n,F_(r))=Θ(n^(r)).Our result in particular generates infinitely many new Turán exponents.As a byproduct,we formulate a framework that is taking shape in recent work on the Bukh–Conlon conjecture.
基金Shanxi provice scientific facilities and instruments shared service platform of magnesium-based matierals electric impulse aided forming(201805D141005)National Natural Science Foundation of China(51404166,51704209,U1810208)+3 种基金Science and Technology Major Project of Shanxi province(20191102008,20191102007,20181101008)Natural Science Foundation of Shanxi Province(201701D121045)Shanxi Province Science Foundation for Youths(2016021063)The Projects of International Cooperation in Shanxi(201803D421086).
文摘The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.
