A nonincreasing sequence ( of n nonnegative integers is said to be graphic if it is the degree sequence of a simple graph G of order n. The set of all graphic sequences of n terms with even sum 2m and trace f is a pos...A nonincreasing sequence ( of n nonnegative integers is said to be graphic if it is the degree sequence of a simple graph G of order n. The set of all graphic sequences of n terms with even sum 2m and trace f is a poset G_(n,m,f) under majorization relation. The paper characterizes the minimal elements in the poset G_(n,m,f) and determines the number of minimal elements in various posets of graphic sequences.展开更多
We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with...We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with this situation we study certain aspects of best approximation of elements of a unital C*-algebra by elements of a unital C*-subalgebra.展开更多
The modified version of Yahalom protocol improved by Burrows, Abradi, and Needham （BAN） still has security drawbacks. This study analyzed such flaws in a detailed way from the point of strand spaces, which is a nove...The modified version of Yahalom protocol improved by Burrows, Abradi, and Needham （BAN） still has security drawbacks. This study analyzed such flaws in a detailed way from the point of strand spaces, which is a novel method of analyzing protoeol＇s security. First, a mathematical model of BAN-Yahalom protocol is constructed. Second, penetrators＇ abilities are restricted with a rigorous and formalized definition. Moreover, to increase the security of this protocol against potential attackers in practice, a further improvement is made to the protocol. Future application of this re-improved protocol is also discussed.展开更多
文摘A nonincreasing sequence ( of n nonnegative integers is said to be graphic if it is the degree sequence of a simple graph G of order n. The set of all graphic sequences of n terms with even sum 2m and trace f is a poset G_(n,m,f) under majorization relation. The paper characterizes the minimal elements in the poset G_(n,m,f) and determines the number of minimal elements in various posets of graphic sequences.
基金supported in part by US National Science Foundation (Grant No. DMS-0753228)
文摘We show that if B is a C*-subalgebra of a C*-algebra A such that B contains a bounded approximate identity for A,and if L is the pull-back to A of the quotient norm on A/B,then L is strongly Leibniz.In connection with this situation we study certain aspects of best approximation of elements of a unital C*-algebra by elements of a unital C*-subalgebra.
基金supported by the National Natural Science Foundation of China(6057314,60773041)
文摘The modified version of Yahalom protocol improved by Burrows, Abradi, and Needham （BAN） still has security drawbacks. This study analyzed such flaws in a detailed way from the point of strand spaces, which is a novel method of analyzing protoeol＇s security. First, a mathematical model of BAN-Yahalom protocol is constructed. Second, penetrators＇ abilities are restricted with a rigorous and formalized definition. Moreover, to increase the security of this protocol against potential attackers in practice, a further improvement is made to the protocol. Future application of this re-improved protocol is also discussed.
