采用有限体积法和自适应网格技术,对超椭圆颗粒群在粘性、不可压流场中的绕流过程进行了数值模拟。在3≤Re≤200, 0.303≤k≤0.836 and 2≤n≤5的工况下,研究了雷诺数(Re)、孔隙率(k)和形状指数(n)对颗粒群绕流过程中的流动特性(流线分...采用有限体积法和自适应网格技术,对超椭圆颗粒群在粘性、不可压流场中的绕流过程进行了数值模拟。在3≤Re≤200, 0.303≤k≤0.836 and 2≤n≤5的工况下,研究了雷诺数(Re)、孔隙率(k)和形状指数(n)对颗粒群绕流过程中的流动特性(流线分布和速度矢量)、阻力特性(阻力系数C_d)和传热特性(平均努塞尔数Nu)的影响。结果表明,随着Re从3增大至200,超椭圆颗粒群中的C_d逐渐减小,而Nu逐渐增大。同样,随着k的增大,C_d先急剧减小,当k超过某一临界值时,C_d趋于稳定,而Nu逐始终随k的增大而增大。此外,无论n如何变化,e始终与k呈正相关,并在n=2时达到最大值。展开更多
利用虚数乘法(Com p lex M u ltip lication,CM)生成Fp上的椭圆曲线,通常只使用虚二次域的最大整环.本文将虚二次域的部分环也用于Fp上的椭圆曲线的生成上,这样由于Pe ll方程u2+d v2=4p在Z/2p,Z/3p上也存在解,在同样判别式范围内可以生...利用虚数乘法(Com p lex M u ltip lication,CM)生成Fp上的椭圆曲线,通常只使用虚二次域的最大整环.本文将虚二次域的部分环也用于Fp上的椭圆曲线的生成上,这样由于Pe ll方程u2+d v2=4p在Z/2p,Z/3p上也存在解,在同样判别式范围内可以生成更多的椭圆曲线,经M athem atica编程计算,生成的曲线数量有明显增加.展开更多
The idea behind a (t, n) threshold blind signature is that a user can ask at least t out of n players of a group to cooperate to generate a signature for a message without revealing its content. This paper first prese...The idea behind a (t, n) threshold blind signature is that a user can ask at least t out of n players of a group to cooperate to generate a signature for a message without revealing its content. This paper first presents a new blind signature scheme from Weil pairing on elliptic curves. Based on this scheme, a threshold blind signature scheme is proposed. It is efficient and has the security properties of robustness and unforgeability. In the proposed scheme, the group manger is introduced to take the role of distributing the group secret key to each player. However, he cannot forge the players to generate partial blind signatures (Each partial blind signature depends on not only the secret key of the player, but also a random number the player picks). Compared with a threshold signature with a trusted third party, its advantage is obvious; Compared with a threshold signature without a trusted third party, it is more simple and efficient.展开更多
In this paper,we use the method of representation of Lie group to study a class of nonhomoge- neous convolution operator on the nilpotent Lie group H^M×R^k,and give a criteerion of their hypoellipticity.
In this paper, the Almgren＇s frequency function of the following sub-elliptic equation with singular potential on the Heisenberg group：-Cu＋V（z,t）u=Xi（aij（z,t）Xju）＋V（z,t）u=0 is introduced. The monotonicity ...In this paper, the Almgren＇s frequency function of the following sub-elliptic equation with singular potential on the Heisenberg group：-Cu＋V（z,t）u=Xi（aij（z,t）Xju）＋V（z,t）u=0 is introduced. The monotonicity property of the frequency is established and a doubling condition is obtained. Consequently, a quantitative proof of the strong unique continuation property for such equation is given.展开更多
As a generalization to the heat semigroup on the Heisenberg group, the diffusion semigroup generated by the subelliptic operator L :=1/2 sum from i=1 to m X_i^2 on R^(m+d):= R^m× R^d is investigated, where X_i(x...As a generalization to the heat semigroup on the Heisenberg group, the diffusion semigroup generated by the subelliptic operator L :=1/2 sum from i=1 to m X_i^2 on R^(m+d):= R^m× R^d is investigated, where X_i(x, y) = sum (σki?xk) from k=1 to m+sum (((A_lx)_i?_(yl)) from t=1 to d,(x, y) ∈ R^(m+d), 1 ≤ i ≤ m for σ an invertible m × m-matrix and {A_l}_1 ≤ l ≤d some m × m-matrices such that the Hrmander condition holds.We first establish Bismut-type and Driver-type derivative formulas with applications on gradient estimates and the coupling/Liouville properties, which are new even for the heat semigroup on the Heisenberg group; then extend some recent results derived for the heat semigroup on the Heisenberg group.展开更多
文摘采用有限体积法和自适应网格技术,对超椭圆颗粒群在粘性、不可压流场中的绕流过程进行了数值模拟。在3≤Re≤200, 0.303≤k≤0.836 and 2≤n≤5的工况下,研究了雷诺数(Re)、孔隙率(k)和形状指数(n)对颗粒群绕流过程中的流动特性(流线分布和速度矢量)、阻力特性(阻力系数C_d)和传热特性(平均努塞尔数Nu)的影响。结果表明,随着Re从3增大至200,超椭圆颗粒群中的C_d逐渐减小,而Nu逐渐增大。同样,随着k的增大,C_d先急剧减小,当k超过某一临界值时,C_d趋于稳定,而Nu逐始终随k的增大而增大。此外,无论n如何变化,e始终与k呈正相关,并在n=2时达到最大值。
文摘利用虚数乘法(Com p lex M u ltip lication,CM)生成Fp上的椭圆曲线,通常只使用虚二次域的最大整环.本文将虚二次域的部分环也用于Fp上的椭圆曲线的生成上,这样由于Pe ll方程u2+d v2=4p在Z/2p,Z/3p上也存在解,在同样判别式范围内可以生成更多的椭圆曲线,经M athem atica编程计算,生成的曲线数量有明显增加.
基金Supported by the National 973 Project of China(No.G1999035803)the National Natural Science Foundation of China (No.60373104)the National 863 Project of China (No.2002AA143021)
文摘The idea behind a (t, n) threshold blind signature is that a user can ask at least t out of n players of a group to cooperate to generate a signature for a message without revealing its content. This paper first presents a new blind signature scheme from Weil pairing on elliptic curves. Based on this scheme, a threshold blind signature scheme is proposed. It is efficient and has the security properties of robustness and unforgeability. In the proposed scheme, the group manger is introduced to take the role of distributing the group secret key to each player. However, he cannot forge the players to generate partial blind signatures (Each partial blind signature depends on not only the secret key of the player, but also a random number the player picks). Compared with a threshold signature with a trusted third party, its advantage is obvious; Compared with a threshold signature without a trusted third party, it is more simple and efficient.
文摘In this paper,we use the method of representation of Lie group to study a class of nonhomoge- neous convolution operator on the nilpotent Lie group H^M×R^k,and give a criteerion of their hypoellipticity.
基金supported by the National Natural Science Foundation of China(Nos.10931005,11371076)
文摘In this paper, the authors study the homologically trivial symplectic group actions on homotopy elliptic surfaces E(n) and get some rigidity results.
基金Project supported by the National Natural Science Foundation of China (Nos. 11071119, 11101132)
文摘In this paper, the Almgren＇s frequency function of the following sub-elliptic equation with singular potential on the Heisenberg group：-Cu＋V（z,t）u=Xi（aij（z,t）Xju）＋V（z,t）u=0 is introduced. The monotonicity property of the frequency is established and a doubling condition is obtained. Consequently, a quantitative proof of the strong unique continuation property for such equation is given.
基金supported by National Natural Science Foundation of China(Grant Nos.11131003 and 11431014)the 985 Project and the Laboratory of Mathematical and Complex Systems
文摘As a generalization to the heat semigroup on the Heisenberg group, the diffusion semigroup generated by the subelliptic operator L :=1/2 sum from i=1 to m X_i^2 on R^(m+d):= R^m× R^d is investigated, where X_i(x, y) = sum (σki?xk) from k=1 to m+sum (((A_lx)_i?_(yl)) from t=1 to d,(x, y) ∈ R^(m+d), 1 ≤ i ≤ m for σ an invertible m × m-matrix and {A_l}_1 ≤ l ≤d some m × m-matrices such that the Hrmander condition holds.We first establish Bismut-type and Driver-type derivative formulas with applications on gradient estimates and the coupling/Liouville properties, which are new even for the heat semigroup on the Heisenberg group; then extend some recent results derived for the heat semigroup on the Heisenberg group.
