一类余维3的鞍-焦点异宿环分支

对余维3系统X_μ(x)具有包含一个双曲鞍-焦点O_1和一个非双曲鞍-焦点O_2的异宿环f进行了研究.证明了在f的邻域内有可数无穷条周期轨线和异宿轨线,当非粗糙异宿轨线Γ~0破裂时X_μ(x)会产生同宿轨分支,并给出了相应的分支曲线和两种同宿环共存的参数值.在3参数扰动下Γ~0破裂和O_2点产生Hopf分支的情况下,在f的邻域内有一条含O_1点同宿环,可数无效多条的轨线同宿于O_2点分支出的闭轨H_0,一条或无穷多条(可数或连续统的)异宿轨线等.     

弱Silnikov现象中的全局分支问题

本文考虑在一条同宿于具一对纯虚特征值的鞍－焦点的轨道邻域内的分支问题，证明了在同宿分支值的邻域内，存在着可数无穷多个鞍结点分支值，倍周期分支值和２－脉冲同宿分支值，并且两相邻鞍结点分支值的比趋于常数１。     

一类3维反转系统中的异维环分支

研究了一类3维反转系统中包含2个鞍点的对称异维环分支问题, 且仅限于研究系统的线性对合R的不变集维数为1的情形. 给出了R-对称异宿环与R-对称周期轨线存在和共存的条件, 同时也得到了R-对称的重周期轨线存在性. 其 次, 给出了异宿环、 同宿轨线、 重同宿轨线和单参数族周期轨线的存在性、 唯一性和共存性等结论, 并且发现不可数无穷条周期轨线聚集在某一同宿轨线的小邻域内. 最后给出了相应的分支图.     

三维反转系统中余维2和3的异维环分支

研究了三维反转系统中具有2个鞍点的对称异维环分支问题.在此反转性意味着存在线性对合R,使得系统在R变换和时间逆向条件下仍保持不变.当R的不动点构成集合的维数dim Fix(R)=1时,我们研究了R-对称异维环,R-对称周期轨线,同宿环,重周期轨线和具有单参数族的无穷条周期轨线的存在性及它们的共存性.本文也明确得到了对称异维环的重同宿分支,且分支出的不可数无穷条周期轨道聚集在某条同宿轨道的小邻域内.进一步,作者也证明了相应的分支曲面及其存在区域.对于dim Fix(R)=2时的情形,本文得到了系统可分支出R-周期轨道和R-对称异宿环.     

三点粗异宿环分支

本文研究高维系统连接三个鞍点的粗异宿环的分支问题.在一些横截性条件和非扭曲条件下,获得了Γ附近的1-异宿三点环, 1-异宿两点环、 1-同宿环和1-周期轨的存在性,唯一性和不共存性.同时给出了分支曲面和存在域.上述结果被进一步推广到连接l个鞍点的异宿环的情况,其中l≥2.     

R~n中具有非双曲奇点的异宿分支

考虑具有两个非双曲奇点的n维异宿系统。对这类Rⁿ中的高余维分支问题,求得Melnikov型向量分支函数,以保证在两个非双曲奇点所分裂出的新奇点间存在异宿轨线。     

连接1阶细鞍焦点的反转同宿环附近的动态及分支问题

在反转条件下研究了连接1阶细鞍焦点的对称同宿轨线附近包括具有各种不同缠绕数的周期轨线和同宿轨线在内的极其复杂的轨线结构,并且讨论了伴随Hopf分支的同宿轨线分支情况.     

分段光滑系统中同宿环附近的极限环分支（英文）

在对机械、工程、生物等的实际应用中,非光滑动力系统的理论研究已经被广泛应用.本文将同宿分支在光滑动力系统中的研究结果推广到分段光滑动力系统中.假设平面分段光滑动力系统中存在一个含有双曲鞍点的分片光滑的同宿环,并且在同宿环内有一族闭轨.通过计算一阶Melnikov函数的展开式系数得出同宿环在扰动过后产生的极限环的个数.     

任意有限维空间中鞍焦点同宿环的稳定性

在改造和扩充空间同宿环的部分邻域稳定性定义的基础上,通过建立首次回归映射并考虑其压缩性和扩张性,对任意有限维空M系统连接双曲鞍焦点的同宿环的稳定性质作了深入的研究,包括在不同的主特征值条件下给出了在其管状邻域内稳定集合(流形)和不稳定集合(流形)的存在性及其维数.     

带有倾斜翻转的余维2反转异宿分支

本文运用由Zhu和Xia于1998年建立的方法,详细研究了一个四维反转系统中带有倾斜翻转的异宿环分支问题,取得了一系列有意义的结果．例如：R-对称同宿轨道的存在性、R-对称同宿轨道与R-对称异宿轨道、R-对称同宿轨道与R-对称周期轨道的共存性,并找到了反转异宿轨道分支中的R-对称倍同宿轨道分支（即：二重R-对称同宿分支）、收敛于同宿轨道的无穷多R-对称同宿轨道的存在性,最后给出了相关的分支曲面和存在区域．     

Determining a Rotation of a Tetrahedron from a Projection

The following problem, arising from medical imaging, is addressed: Suppose that T is a known tetrahedron in ?³ with centroid at the origin. Also known is the orthogonal projection U of the vertices of the image ?T of T under an unknown rotation ? about the origin. Under what circumstances can ? be determined from T and U?     

On a mapping of a projective space into a sphere

We obtain an exact estimate for the minimum multiplicity of a continuous finite-to-one mapping of a projective space into a sphere for all dimensions. For finite-to-one mappings of a projective space into a Euclidean space, we obtain an exact estimate for this multiplicity for n = 2, 3. For n ≥ 4, we prove that this estimate does not exceed 4. Several open questions are formulated.     

Calculating a function of a matrix with a real spectrum

Let T be a square matrix with a real spectrum, and let f be an analytic function. The problem of the approximate calculation of f(T) is discussed. Applying the Schur triangular decomposition and the reordering, one can assume that T is triangular and its diagonal entries t_ii are arranged in increasing order. To avoid calculations using the differences t_ii ? t_jj with close (including equal) t_ii and t_jj, it is proposed to represent T in a block form and calculate the two main block diagonals using interpolating polynomials. The rest of the f(T) entries can be calculated using the Parlett recurrence algorithm. It is also proposed to perform some scalar operations (such as the building of interpolating polynomials) with an enlarged number of significant decimal digits.

     

Evolution to a steady state for a rarefied gas flowing from a tank into a vacuum through a plane channel

A kinetic equation (S-model) is used to solve the nonstationary problem of a monatomic rarefied gas flowing from a tank of infinite capacity into a vacuum through a long plane channel. Initially, the gas is at rest and is separated from the vacuum by a barrier. The temperature of the channel walls is kept constant. The flow is found to evolve to a steady state. The time required for reaching a steady state is examined depending on the channel length and the degree of gas rarefaction. The kinetic equation is solved numerically by applying a conservative explicit finite-difference scheme that is firstorder accurate in time and second-order accurate in space. An approximate law is proposed for the asymptotic behavior of the solution at long times when the evolution to a steady state becomes a diffusion process.