双重介质储集层系统的参数辨识问题

本文研究了双重介质储集层的历史匹配问题、均质地层的双介质系统的可辨识性和可观测性问题。得到了泛函对辨识的参数的Fréchet导数公式,这是用任何一种共轭梯度法或梯度法计算辨识的参数所必须的公式。给出了均质地层的双介质储集层系统的可辨识性条件和可观测性的充分必要条件。     

缺项算子矩阵的幂等补

本文获得各类二阶缺项算子矩阵存在幂等补的充分必要条件,并且给出它们各自所有幂等补的参数表示形式．     

分布参数系统辨识的必要条件(英文)

考虑了辨识下列方程中算子值参数Ｂ的必要条件,代价泛函为：证明了：最佳估计Ｂ０由一个优化系统确定,而该优化系统由状态方程、伴随方程和优化条件组成．     

方差分量的非负二次同时估计的可容许性

设方差分量模型，其中β∈为未知参数，Ｘ已知，Ｖ１≥０，Ｖ２≥０为已知的非负定矩阵．文［１］在一定的条件下给出了非负二次估计可容许的一个充分必要条件．但必要条件是在ｘ＝Ｉｎ（单位矩阵），Ｖ１＝Ｖ２＞０的条件下给出的，由于这些限制使必要条件不理想．本文去掉了这些限制，对一般的方差分量模型，给出了与文［１］中一样的必要条件，同时也研究了非齐次二次估计的可容许性．     

一类非光滑分布参数系统的可辨识性及最优性条件

变压器温度场参数辨识问题是一种分片光滑的分布参数辨识问题,以流速为辨识参数,针对传质传热的一类分布参数系统参数辨识问题,证明了系统最优参数的存在性和控制参数为最优的必要条件,为变压器温度场的数值模拟研究提供了理论基础.     

PBIB设计的约化

设Ｄ是一个有ｍ个结合类的ＰＢＩＢ设计，且它的参数λ１，λ２，．．．，λｍ中至少有两个是相等，第二节中，给出了ＰＢＩＢ设计Ｄ可以用遂次合并结合类来约化的充分必要条件，第三节给出了ＰＢＩＢ设计Ｄ可以用同时合并结合来约化的充分必要条件，最后，在第四节里我们研究了上述两种方法之间的关系。     

Pritchard-Salamon系统的可稳定化性和代数Riccati方程

在本文中,我们给出了光滑Pritchard－Salamon系统（简称PS系统）能以紧算子为可容反馈可稳定化的充分必要条件．应用此结果,我们给出了光滑PS系统中的代数Riccati方程的所有非负自伴解的参数化表示,把[1]中的主要结果推广到了光滑PS系统．     

关于Orlicz空间的H性质的注记

该文给出了Orlicz函数空间具有H性质的充分必要条件．     

二次型之比服从F—分布的充分必要条件

考察F－分布的密度和矩，本文给出了正态随机向量二次型之比服从F－分布的充分必要条件，进而给出了椭球等高随机向量二次型之比服从F分布的充分必要条件．作为应用，我们减弱了传统F－检验中对两简单子样独立性的要求．     

关于Prufer环的特征刻画

本文用可除模给出了Ｐｒｕｆｅｒ环的一个充分必要条件．     

双曲型守恒律方程的熵稳定格式的一些讨论

本文讨论双曲型守恒律方程的熵稳定格式.对于给定的熵对,格式所满足的熵条件中的数值熵通量是不唯一的.Tadmor的充分条件可以唯一地确定标量方程的熵守恒通量,但不能唯一确定方程组的熵守恒通量,却可以给出方程组的空间一阶精度的熵守恒格式.也讨论了在熵守恒通量上添加数值粘性得到的显式熵稳定格式需要满足的条件及常见的时间离散对熵守恒和熵稳定的影响.     

感应电动机磁链跟踪问题

首先研究了一般非齐次线性时变控制系统状态向量收敛至给定平衡点的充分性条件.进一步讨论了感应电动机磁链控制模型,给出了定子磁链渐近跟踪控制的条件.     

The flux of primary cosmic ray nuclei of atomic numberZ⩾2 at geomagnetic latitude 30°

The method of determining the primary flux of nuclei with atomic number Z?3 developed by Bradt and Peters, has been extended to include all nuclei of charge Z?2. It is shown that the method permits the identification of primary helium nuclei with an efficiencyν?90%. The primary α-particle flux obtained in this way is in very good agreement with that obtained by other methods and the relative flux values for nuclei of atomic number 3?Z?5 and 6?Z?9 agree with previous determinations.     

受扩散与时滞及食物限制影响的人口模型

考虑一类修正的L og istic模型,带有扩散与时滞及非线性的边界条件.利用上下解方法证明解的存在唯一性,当边界流量为负时,0解是渐近稳定的,当边界流量为正时,解在有限时刻达到饱和.     

一类控制系统的渐近跟踪问题

首先研究了一类线性系统渐近跟踪问题的条件 .进一步讨论了感应电动机磁链控制模型 ,给出了定子磁链渐近跟踪控制的条件     

On the Stationary Navier–Stokes Equations in the Half-Plane

We consider the stationary incompressible Navier–Stokes equation in the half-plane with inhomogeneous boundary condition. We prove the existence of strong solutions for boundary data close to any Jeffery–Hamel solution with small flux evaluated on the boundary. The perturbation of the Jeffery–Hamel solution on the boundary has to satisfy a nonlinear compatibility condition which corresponds to the integral of the velocity field on the boundary. The first component of this integral is the flux which is an invariant quantity, but the second, called the asymmetry, is not invariant, which leads to one compatibility condition. Finally, we prove the existence of weak solutions, as well as weak–strong uniqueness for small data and provide numerical simulations.     

An Acceleration Technique for the Augmented IIM for 3D Elliptic Interface Problems

A new fast algorithm based on the augmented immersed interface method and a fast Poisson solver is proposed to solve three dimensional elliptic interface problems with a piecewise constant but discontinuous coefficient. In the new approach, an augmented variable along the interface, often the jump in the normal derivative along the interface is introduced so that a fast Poisson solver can be utilized. Thus, the solution of the Poisson equation depends on the augmented variable which should be chosen such that the original flux jump condition is satisfied. The discretization of the flux jump condition is done by a weighted least squares interpolation using the solution at the grid points, the jump conditions, and the governing PDEs in a neighborhood of control points on the interface. The interpolation scheme is the key to the success of the augmented IIM particularly. In this paper, the key new idea is to select interpolation points along the normal direction in line with the flux jump condition. Numerical experiments show that the method maintains second order accuracy of the solution and can reduce the CPU time by 20-50%. The number of the GMRES iterations is independent of the mesh size.     

A mortar element method for hyperbolic problems

A non-conforming finite element method based on non-overlapping domain decomposition is extended to linear hyperbolic problems. The method is based on streamline-diffusion/discontinuous Galerkin methods and the mortar element method. A weak flux continuity condition at the inflow interface is enforced by means of Lagrange multipliers. This weak flux continuity condition replaces the usual mortar condition for elliptic problems, and allows non-matching grids at the subdomain interfaces. To cite this article: Y. Bourgault, A. El Boukili, C. R. Acad. Sci. Paris, Ser. I 338 (2004).     

Heat flux effect on the droplet entrainment and deposition in annular flow dryout

This paper discusses the internal mass transfer process in annular flow dryout. The emphasis is put on the order of magnitude estimation of respective hydrodynamic and thermal mechanisms and the analysis of the heat flux effect on droplet entrainment and deposition. A simple interfacial turbulence model is developed to characterize the turbulence intensity suppression due to interface tension. The heat flux effect on droplet entrainment depends on the competition between the shear force decrease due to vapor effusion and the bubble emission: in low flow condition, the bubble emission outweighs the shear force decrease, thus the net effect is to increase the droplet entrainment; in high flow condition, the situation may reverse. The heat flux impact on droplet deposition is significant only for very fine droplets (less than 1 μm) because of the coupled effect of interface turbulence damping and the radial vapor effusion due to evaporation, but for droplets of medium and large sizes the heat flux effect is negligible. The analysis is then used to develop constitutive equations for droplet entrainment and deposition rates to take into account the interaction between thermal and hydrodynamic mechanisms, which gives improved CHF prediction for limiting quality regime (LQR) CHF experimental data.