一类离散型奇异积分算子

设｛αｋ｝∞ｋ＝－∞为正数缺项序列，满足ｉｎｆｋαｋ＋１／ｄｋ＝α＞１，Ω（ｙ′）为Ｂｅｓｏｖ空间Ｂ０，１１（Ｓｎ－１）上的函数，其中Ｓｎ－１为Ｒｎ（ｎ２）上的单位球面．本文证明：若∫Ｓｎ－１Ω（ｙ′）ｄσ（ｙ′）＝０，则离散型奇异积分ＴΩ（ｆ）（ｘ）＝∑∞ｋ＝－∞∫Ｓｎ－１ｆ（ｘ－αｋｙ′）Ω（ｙ′）ｄσ（ｙ′）和相关的极大算子ＴΩ（ｆ）（ｘ）＝ｓｕｐＮ∑∞ｋ＝Ｎ∫Ｓｎ－１ｆ（ｘ－αｋｙ′）Ω（ｙ′）ｄσ（ｙ′）均在Ｌ２（Ｒｎ）上有界．上述结果推广了Ｄｕｏａｎｄｉｋｏｅｔｘｅａ和ＲｕｂｉｏｄｅＦｒａｎｃｉａ［１］在Ｌ２情形下的一个结果     

巧用函数单调性解赛题

函数ｆ（ｘ）在区间［ａ,ｂ］上单调增加（或单调减少）,又ｃ、ｄ∈［ａ,ｂ］上,若ｆ（ｃ）＝ｆ（ａ）,则有ｃ＝ｄ．１　求代数式的值例１　已知ｘ、ｙ∈［－π４,π４］,ａ∈Ｒ,且　ｘ３＋ｓｉｎｘ－２ａ＝０４ｙ３＋ｓｉｎｙｃｏｓｙ＋ａ＝０则ｃｏｓ（ｘ＋２ｙ）＝　　．（１９９４年全国高中数学竞赛题）解　由已知条件,可得　　ｘ３＋ｓｉｎｘ＝２ａ（－２ｙ）３＋ｓｉｎ（－２ｙ）＝２ａ故可设函数ｆ（ｔ）＝ｔ３＋ｓｉｎｔ,则有ｆ（ｘ）＝ｆ（－２ｙ）＝２ａ．由于函数ｆ（ｔ）＝ｔ３＋ｓｉｎｔ,在［－π２,π２］上是单…     

方程u_(tt)=u_(xxt) f(u_x)_x初边值问题的差分法

１．引言方程是在国内外引起广泛关注的一类重要的非线性发展方程．文［１］在函数ｆ（ｓ）满足局部 Ｌｉｐ－ｓｃｈｉｔｚ条件及单调性条件（ｆ（ｓ２）－ｆ（ｓ１））（ｓ２－ｓ１）＞ ０的假设下得到了（１．１）初边值问题整体弱解的存在与唯一性;文［２］用 Ｇａｌｅｒｋｉｎ方法,研究了（１．１）的初边值问题,周期边值问题和初值问题,并在函数ｆ’（ｓ）下方有界的假设下得到了整体强解的存在与唯一性． 本文在有限区域 ＱＴ＝［０,１］×［０,Ｔ］（Ｔ＞ ０）上讨论方程（１．１）带有初值条件和边值条件（ｕ（ｘ,ｔ）为未知…     

脉冲中立型时滞微分方程解的振动性

本文讨论一阶脉冲中立型时滞微分方程［ｙ（ｔ）＋Ｐｙ（ｔ－σ）］′＋Ｑ（ｔ）ｙ（ｔ－σ）＝０，ｔ０，ｔ≠ｔｋ，ｋ＝１，２，…，ｙ（ｔ＋ｋ）－ｙ（ｔ－ｋ）＝ｂｋｙ（ｔｋ），ｋ＝１，２，…，｛（Ｅ）这里τ，σ，Ｐ均为常数，τ＞０，σ＞０，Ｑ（ｔ）∈Ｃ（［０，∞），Ｒ＋），ｂｋ＞－１，ｋ＝１，２，…．分三种情况，Ｐ－１；－１＜Ｐ＜０；Ｐ＞０给出了方程（Ｅ）所有解振动的充分条件．     

Riccati微分方程的可积条件

Ｉｎ１９９８,ＺｈａｏＬｉｎｌｏｎｇ［１］ｏｂｔａｉｎｅｄｔｈｅｉｎｔｅｇｒａｂｌｅｃｏｎｄｉｔｉｏｎ：Ｒ＝１αγＰｅ２∫（Ｑ－βＤ）ｄｘ　　　（α,β,γｉｓｃｏｎｓｔ）．（１）ＦｏｒＲｉｃｃａｔｉｅｑｕａｔｉｏｎ：ｙ′＝ｐ（ｘ）ｙ２＋Ｑ（ｘ）ｙ＋Ｒ（ｘ）　　（ＰＲ≠０）．（２）　　Ｈｅｒｅｔｈｅｎｅｗｉｎｔｅｇｒａｂｌｅｃｏｎｄｉｔｉｏｎｓｉｓｇｉｖｅｎ：Ｌ［ｙ０］＝１αγＰｅ２∫（Ｑ＋２ｙ０ｐ－βＤ）ｄｘ．（３）Ｌ［ＡＢ＋ｙ０］＝１αγ（ＡＢ）２Ｌ［ｙ０］ｅ２∫（２ＢＡＬ［ｙ０］＋Ｑ＋２ｙ…     

两类求解y″＝f（x，y）具有极小相位延迟的显式方法

本文提出了两类数值积分二阶周期性初值问题ｙ″＝ｆ（ｘ，ｙ），ｙ（ｘ０）＝ｙ０，ｙ＇（ｘ０）＝ｙ＇０具有极小相位延迟的显式两步法。这些方法推广和改进了文献［１］－［７］中的某些方法。数值试验表明本文中的某些方法优于［１］－［７］中的某些方法。     

一个多线性振荡奇异积分算子

本文建立多线性算子ＴＡ１，Ａ２，…Ａｋｆ（ｘ）＝ｐ．ｖ∫ＲｎｅｉＰ（ｘ，ｙ）Ω（ｘ－ｙ）｜ｘ－ｙ｜ｎ＋Ｍ－ｋｋｊ＝１Ｒｍｊ（Ａｊ；ｘ，ｙ）ｆ（ｙ）ｄｙ，ｎ２，的一个变形的ｓｈａｒｐ估计，其中Ｐ（ｘ，ｙ）是Ｒｎ×Ｒｎ上的实值多项式，Ω是零阶齐性函数且满足某种消失性条件，Ｍ＝∑ｋｊ＝１ｍｊ，Ｒｍｊ（Ａｊ；ｘ，ｙ）表示Ａｊ在ｘ点关于ｙ的ｍｊ阶Ｔａｙｌｏｒ级数余项，对所有满足｜α｜＝ｍｊ－１（ｊ＝１，２，…，ｋ）的指标α，ＤαＡｊ∈ＢＭＯ（Ｒｎ）．作为ｓｈａｒｐ估计的推论，得到了算子ＴＡ１，Ａ２…Ａｋ在Ｌｐ（１＜ｐ＜∞）上的有界性．     

1999年全国高中联赛第三题的简解

题目　已知当ｘ∈［０,１］时,不等式ｘ２ｃｏｓθ－ｘ（１－ｘ）＋（１－ｘ）２ｓｉｎθ＞０恒成立,试求θ的取值范围．这是１９９９年全国高中数学联合竞赛试题第三题,下面给出一种有别于“标准答案”的简单解法．解　若对一切ｘ∈［０,１］,恒有ｆ（ｘ）＝ｘ２ｃｏｓθ－ｘ（１－ｘ）＋（１－ｘ）２ｓｉｎθ＞０,则　ｓｉｎθ＝ｆ（０）＞０,ｃｏｓθ＝ｆ（１）＞０,∴　２ｋπ＜θ＜２ｋπ＋π２,ｋ∈Ｚ．（１）又　ｆ（ｘ）＝（１＋ｓｉｎθ＋ｃｏｓθ）ｘ２－（１＋２ｓｉｎθ）ｘ＋ｓｉｎθ＝（１＋ｓｉｎθ＋ｃｏｓθ）［…     

何以点可以视为圆?

何以点可以视为圆？周传忠（华南师范大学５１０６３１）我们知道，若曲线ｌ：ｆ（ｘ，ｙ）＝０和ｋ：ｇ（ｘ，ｙ）＝０相交，则方程ｆ（ｘ，ｙ）＋λｇ（ｘ，ｙ）＝０表示通过这些交点的一个曲线系．利用这一结论来解一些问题常是很方便的．文［１］、［２］更提出，可以...     

圆锥曲线弦的中点问题的一种简捷解法

求直线被圆锥曲线截得弦的中点问题,是解析几何教学中的一类重要问题;常规解法计算量较大,如何简化其解法一直为人们所关注;文［１］、［２］、［３］等都作过很好的研究;本文介绍一种利用两曲线公共弦方程求解的简捷方法;如图,设Ｐ（ｍ,ｎ）是圆锥曲线ｃ的一条弦ＡＢ的中点,ｃ′是ｃ关于点Ｐ对称的曲线;容易证明,ｃ′的方程为ｆ（２ｍ－ｘ,２ｎ－ｙ）＝０;（见注１）而弦ＡＢ就是曲线ｃ与ｃ′的公共弦;且公共弦ＡＢ所在的直线方程为ｆ（ｘ,ｙ）－ｆ（２ｍ－ｘ,２ｎ－ｙ）＝０（见注２）,从而使问题得到解决;这一方法既适…     

Identification of the Exchange Coefficient from Indirect Data for a Coupled Continuum Pipe-Flow Model

Calibration and identification of the exchange effect between the karst aquifers and the underlying conduit network are important issues in order to gain a better understanding of these hydraulic systems. Based on a coupled continuum pipe-flow （CCPF for short） model describing flows in karst aquifers, this paper is devoted to the identification of an exchange rate function, which models the hydraulic interaction between the fissured volume （matrix） and the conduit, from the Neumann boundary data, i.e., matrix/conduit seepage velocity. The authors formulate this parameter identification problem as a nonlinear operator equation and prove the compactness of the forward mapping. The stable approximate solution is obtained by two classic iterative regularization methods, namely, the Landweber iteration and Levenberg-Marquardt method. Numerical examples on noisefree and noisy data shed light on the appropriateness of the proposed approaches.     

Schrodinger方程的变分迭代解法

该文以Ｓｃｈｒｏｄｉｎｇｅｒ方程为例,分析变分迭代法的一些基本特点．在该方法中引进了一广义拉氏乘子构造了一迭代格式,拉氏乘子可由变分理论最佳识别．由于在识别拉氏乘子是应用了限制变分的概念,所以只能通过迭代才能得到收敛解．为了加快收敛速度,可以在初始近似引入待定常数,而待定常数又可用各种方式最佳识别．文中初步分析了该方法的收敛性,对于Ｓｃｈｒｏｄｉｎｇｅｒ方程,其一阶近似即可得到Ｊｏｓｔ解．     

Existence of Solutions to a Class of Fractional Differential Equations

In this paper, the existence of solutions to a class of fractional differential equations $D_{0+}^{\alpha}u(t)=h(t)f(t, u(t), D_{0+}^{\theta}u(t))$ is obtained by an efficient and simple monotone iteration method. At first, the existence of a solution to the problem above is guaranteed by finding a bounded domain $D_M$ on functions $f$ and $g$. Then, sufficient conditions for the existence of monotone solution to the problem are established by applying monotone iteration method. Moreover, two efficient iterative schemes are proposed, and the convergence of the iterative process is proved by using the monotonicity assumption on $f$ and $g$. In particular, a new algorithm which combines Gauss-Kronrod quadrature method with cubic spline interpolation method is adopted to achieve the monotone iteration method in Matlab environment, and the high-precision approximate solution is obtained. Finally, the main results of the paper are illustrated by some numerical simulations, and the approximate solutions graphs are provided by using the iterative method.     

Morse指数与含Grushin算子的Liouville型定理

本文研究退化椭圆型方程-Δxu-(α+1)2|x|~(2α)Δyu=|u|~(p-1)u,(x,y)∈Rm×Rk和方程-Δxu-(α+1)2|x|~(2α)Δyu=|u|~(p-1)u,(x,y)∈Π的Liouville型定理,其中-Δx-(α+1)2|x|~(2α)Δy是Grushin算子,Π={(x,y)∈Rm×Rk:x10}或{(x,y)∈Rm×Rk:y10}.本文将证明,当1p(Q+2)/(Q-2)时,上述方程Morse指数有限的有界解只有零解,其中Q=m+(α+1)k为齐次空间的维数,因此,本文将Laplace方程的结果推广到含Grushin算子的方程.     

求解非定常Lavrentiev迭代方程的多尺度配置法

本文采用多尺度配置法求解第一类弱扇形积分方程.将压缩配置法用于投影离散非定常迭代正则化方程,得到了近似解在Banach空间范数下误差估计,给出了迭代停止准则,确保近似解无穷范数下的最优收敛率.优点是确保了收敛率,减少了计算量.数值例子验证了算法的有效性.     

Approximation Solutions of Nonlinear Strongly Accretive Operator Equations by Ishikawa Iteration Procedure with Errors

Let 1＜ρ≤2,E be a real ρ-uniformly smooth Banach space and T:E→E be a continuous and strongly accretive operator.The purpose of this paper is to investigate the problem of approximating solutions to the equation Tx=f by the Ishikawa iteration procedure with errors (?) where x_0 ∈ E,{u_n},{υ_n}are bounded sequences in E and{α_n},{b_n},{c_n},{a_n~'},{b_n~'},{c_n~'} are real sequences in[0,1].Under the assumption of the condition 0＜α≤b_n c_n,An≥0, it is shown that the iterative sequence{x_n}converges strongly to the unique solution of the equation Tx=f.Furthermore,under no assumption of the condition(?)(b_n~' c_n~')=0,it is also shown that{x_n}converges strongly to the unique solution of Tx=f.     

关于m-增生算子的Ishikawa迭代程序的收敛性与稳定性

在任意的Banach空间的条件下,具误差的Ishikawa迭代程序强收敛到非线性方程x+Tx=f的唯一解并且是几乎稳定的.其结果推广、改进和统一了Zeng和Liu的相关结果.     

An iterative method based on equation decomposition for the fourth‐order singular perturbation problem

In this article, we propose an iterative method based on the equation decomposition technique ( 1 ) for the numerical solution of a singular perturbation problem of fourth‐order elliptic equation. At each step of the given method, we only need to solve a boundary value problem of second‐order elliptic equation and a second‐order singular perturbation problem. We prove that our approximate solution converges to the exact solution when the domain is a disc. Our numerical examples show the efficiency and accuracy of our method. Our iterative method works very well for singular perturbation problems, that is, the case of 0 < ε ? 1, and the convergence rate is very fast. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2013     

一类Riccati矩阵方程广义自反解的双迭代算法

本文研究了一类Riccati矩阵方程广义自反解的数值计算问题.利用牛顿算法将Riccati矩阵方程的广义自反解问题转化为线性矩阵方程的广义自反解或者广义自反最小二乘解问题,再利用修正共轭梯度法计算后一问题,获得了求Riccati矩阵方程的广义自反解的双迭代算法.拓宽了求解非线性矩阵方程的迭代算法.数值算例表明双迭代算法是有效的.     

Projected equation methods for approximate solution of large linear systems

We consider linear systems of equations and solution approximations derived by projection on a low-dimensional subspace. We propose stochastic iterative algorithms, based on simulation, which converge to the approximate solution and are suitable for very large-dimensional problems. The algorithms are extensions of recent approximate dynamic programming methods, known as temporal difference methods, which solve a projected form of Bellman’s equation by using simulation-based approximations to this equation, or by using a projected value iteration method.