侧向局部加热对流的周期性

通过流体力学方程组的数值模拟,研究了侧向局部加热条件下Prandtl数Pr=0.0272时流体对流的周期性.结果表明:随着Grashof数Gr的增加,对流按稳态对流、单局部周期对流、双局部周期对流、准周期对流的顺序发展.当Gr<3.6×103时,对流为稳态;在3.6×103相似文献   

由曲率函数和外力场之差支配的凸超曲面的发展

考虑由曲率函数和外力场之差支配的凸超曲面的发展.证明了外力场为常向量场时,初始超曲面的凸性是保持的,且曲率流在有限时间内爆破.对于线性外力场,初始超曲面的凸性保持.而且,若线性常数为负数,则曲率流在有限时间内收敛到一点;若线性常数为正数且初始曲率小于某一与外力场有关的常数,则曲率流光滑地存在于任意有限时间区间,并发散到无穷;若线性常数为正数且初始曲率大于某一与外力场有关的常数,则曲率流在有限时间内爆破.     

Faithful Transfer Arbitrary Pure States with Mixed Resources

In this paper, we show that some special mixed quantum resource experience the same property of pure entanglement such as Bell state for quantum teleportation. It is shown that one mixed state and three bits of classical communication cost can be used to teleport one unknown qubit compared with two bits via pure resources. The schemes are easily implement with model physical techniques. Moreover, these resources are also optimal and typical for faithfully remotely prepare an arbitrary qubit, two-qubit and three-qubit states with mixed quantum resources. Our schemes are completed as same as those with pure quantum entanglement resources except only 1 bit additional classical communication cost required. The success probability is independent of the form of the mixed resources.     

Global well-posedness and the classical limit of the solution for the quantum Zakharov system

In this paper, we study the quantum Zakharov system, which describes the nonlinear interaction between the quantum Langmuir and quantum ion-acoustic waves. The global well-posedness result of this system in the energy and above energy spaces is obtained in the case d = 1, 2, 3. Moreover, the classical limit behavior of the quantum Zakharov system is also investigated as the quantum parameter tends to zero.     

逐段单调函数迭代根的不存在性

对于一类非单调连续映射,即逐段单调函数,当它存在特征区间时,结果是丰富的.本文讨论的是相反的情形,也就是不存在特征区间的时候.本文部分回答了文章[Ann. Polon. Math., 1997, 65(2): 119--128]中的公开问题一.     

Permanence and periodic solutions for a class of delay Nicholson’s blowflies models

This paper covers the dynamic behaviors for a class of Nicholson’s blowflies models with a nonlinear density-dependent mortality term. By using inequality analyze technique and coincidence degree theory, some sufficient conditions are determined that guarantee the permanence of the model and the existence of positive periodic solutions. Moreover, we give an example to illustrate our main results.     

Almost periodic solution for Nicholson’s blowflies model with patch structure and linear harvesting terms

In this paper, we study the existence and exponential convergence of positive almost periodic solutions for a class of Nicholson’s blowflies model with patch structure and multiple linear harvesting terms. Under appropriate conditions, we establish some criteria to ensure that the solutions of this system converge locally exponentially to a positive almost periodic solution. Moreover, we give some examples and numerical simulations to illustrate our main results.     

奇异摄动问题内罚间断有限方法的最优阶一致收敛性分析

本文在Bakhvalov-Shishkin网格上分析了采用高次元的内罚间断有限元方法求解一维对流扩散型奇异摄动问题的最优阶一致收敛性. 取k(k≥1)次分片多项式和网格剖分单元数为N时,在能量范数度量下, Bakhvalov-Shishkin网格上可获得O(N^-k)的一致误差估计. 在数值算例部分对理论分析结果进行了验证.     

Atom diffusion in furnaces — models and measurements

Experimental as well as the theoretical approach to estimate diffusion coefficients for several analyte elements with different behavior in graphite furnaces, lead, gold, indium and chromium, were investigated. ‘Close’ graphite furnaces of two designs differing in the size of end apertures and the diameter of the injection port were used. The furnaces were fast heated at rates of approximately 10 000 K s⁻¹. The peak absorbance of all studied analytes was independent of geometry, suggesting that the separation of atomization and removal was attained. Residence times of the analytes in the two different furnaces were determined from absorbance tail shapes. In the case of gold, the influence of temperature in the range between 1800 and 2200 K on the residence time in both furnaces was also found. The residence times measured in the two different furnaces under otherwise identical conditions, made possible to select the accurate model of diffusional removal from several possible models. The knowledge of the accurate model allowed the estimate of experimental diffusion coefficients. They were thus compared with those semiempirically calculated from kinetic theory of gases, extended to allow for the intermolecular forces. The accuracy of these calculations is limited since the input data (critical temperatures, boiling temperature or melting temperature, molal volumes at the critical, boiling and melting points, metallic crystallographic radii and dissociation constants of metal dimers) are not known with adequate accuracy. The comparison of ‘theoretical’ and ‘experimental’ values of diffusion coefficients makes possible to assess value of using individual sources of input data for the semiempirical calculations.