二阶奇异非线性微分方程边值问题的正解

分别在0≤f₀+<M₁,m₁<f_∞-≤∞和0≤f_∞+<M₁,m₁<f₀-≤∞的情形下研究了非线性奇异边值问题u″+g(t)f(u)=0,0<t<1,αu(0)-βu′(0)=0,γu(1)+δu′(1)=0正解的存在性,其中f₀+=₀f(u)/u,f_∞-=_∞f(u)/u,f₀-=₀f(u)/u,f_∞+=_∞f(u)/u,g在区间[0,1]的端点可以具有奇性。     

一类带约束的二维弱奇异积分方程的解*

本文找出二维弱奇异第一类积分方程作用着约束方程的解p.p=p(r,θ)={2/[π2k(φ₀]}√F(r,θ)-c_*(0≤r≤r_*)其中是(s,φ)原点在M(r,θ)的局部极坐标,(r,θ)是原点在O(0,0)的总体极坐标:k和F是给出的连续函数;φ₀是一常数;F(_*,θ)=c_*(常数)是研究域Q的边界围线。所用方法可推广到三维情形。     

一类带约束的二维弱奇异积分方程的一般解及其应用*

本文给出二维弱奇异积分方程作用着约束方程的比[1]为更一般的解P式中k和产是给出的连续函数;(s,φ)是原点在M(r,θ)的局部极坐标;(r,θ)是原点在O(0.0)的总体极坐标;F(r_*,θ)=c_*(常数)是研究域Q的边界围线?Q:g(ω)=F(r,θ)/[πkφ₀];g'=dg/dω,ω=N-r2sin2(θ+φ₀);φ₀,N为中值.[1]的(2.19)型的解仅为F(r,θ)=ω时上述解的特例.文中给出刚性圆锥和弹性半空间接触问题的解作为应用例子.此解较Love(1939)的解简明.     

自反矩阵与反自反矩阵的广义逆特征值问题

1引言在振动设计中,往往需要修改一个系统的数学模型的物理参数,这在数学上可以归结为矩阵的逆特征值问题或广义逆特征值问题（见[1]）.例如,下面给出振动系统中刚度矩阵与质量矩阵的校正问题.设ω₁,ω₂,…,ω_m（m≤n）是m个自然频率,φ₁,φ₂,…,φ_m是相应的振型,令Ω²=diag（ω₁²,ω₂²,…,ω_m²）,φ=（φ₁,φ₂,…,φ_m）.设K为待校正的刚度矩阵,M为待校正的质量矩阵,它们满足下列条件（1.1）特征方程Kφ=MφΩ²,     

非线性分数次边值问题改进的ADM解法(英文)

We use the modified Adomian decomposition method（ADM） for solving the nonlinear fractional boundary value problem {D（^α₀） + u（x） = f（x, u（x））, 0 < x < 1, 3 < α≤ 4 u（0） = α₀ , u’’ （0） = α₂ u（1） = β₀ , u’’（1） = β₂} （1） where D（₀^α）+u is Caputo fractional derivative and α₀,α₂,β₀,β₂ is not zero at all,and f:[0,1]×R→ R is continuous.The calculated numerical results show reliability and efficiency of the algorithm given.The numerical procedure is tested on linear and nonlinear problems.     

非线性变厚度球壳正压力下有矩解

本文对工程上常用的非线性变厚度(厚度方程为δ=δ₀(1+βφ)2)的球壳正压力下有矩问题给出内力的欧拉形解答.     

自伴标准算子代数上强保持k-斜交换性映射的刻画

令H是维数大于2的复Hilbert空间,A是H上自伴标准算子代数.对于给定的正整数k≥1,H上算子A与B的k-斜交换子递推地定义为_*[A,B]_k=_*[A,_*[A,B]_k-1],其中_*[A,B]₀=B,_*[A,B]₁=AB-BA^*.设k≥4,φ是A上的值域包含所有一秩投影的映射.本文证明了φ满足_*[φ（A）,φ（B）]_k=_*[A,B]_k对任意A,B∈A都成立的充分必要条件是φ（A）=A对任意A∈A都成立,或φ（A）=-A对任意A∈A都成立.当k是偶数时后一情形不出现.     

阻尼板振动方程的紧致差分方法

<正>1引言考虑如下阻尼板振动方程初边值问题■其中?=(0, a)×(0, b)?R², T是时间总量,■μ(μ> 0)为阻尼系数,ρ为给定正常数, f (x, y, t)是已知函数,φ₁(x, y)和φ₂(x, y)是初值函数,ψ₁(y, t),ψ₂(y, t),ψ₃(x, t),ψ₄(x, t)和g₁(y, t), g₂(y, t), g₃(x, t), g₄(x, t)是边值函数.     

拟周期系统的Floquet理论

在这篇文章,我们对拟周期系统dx/dt=A(ω₁t,ω₂t.…,ω_mt)x (0.1)建立了Floquet理论.其中n×n方阵A(u₁,u₂,…,u_m)是u₁,u₂,…,u_m以2π为周期的周期方阵,同时假定A(u₁,u₂,…,u_m)∈Cτ,τ=(N+1)τ₀,τ₀=2(m+1),N=1/2n(n+1).我们定义了(0.1)的特征指数根β₁,β₂,…,β_n,假设下式成立:其中K(ω),K(ω,β)>0,k_μ,i_v是整数,k₁,k₂…,k_m不全为零:i2=-1.那末有拟周期线性变换,把(0.1)化为常系数的线性系统.     

非线性边值问题的奇摄动

本文研究边值问题:εy"=f(x,y,y',ε,μ)(μ0(ε,μ)y(x,ε,μ)|(x=1-μ)=φ₁(ε,μ)其中ε,μ是两个正的小参数 在f_y’≤-k<0和其他适当的限制下,存在一个解且满足其中y₀,0(x)是退化问题 f(x,y,y',0,0)=0(01(0,0)的解,而y_i-j,j(x)(j=0,1,…,i;i=1,2,…m)能够从某些线性方程逐次求得.     

Single-Phase averaging for the Ablowitz-Ladik chain

The Bogolyubov-Whitham averaging method is applied to the Ablowitz-Ladik chain $$ \begin{gathered} - i\dot q_n - (1 - q_n r_n )(q_{n - 1} + q_{n + 1} ) + 2q_n = 0, \hfill \\ - i\dot r_n + (1 - q_n r_n )(r_{n - 1} + r_{n + 1} ) + 2r_n = 0 \hfill \\ \end{gathered} $$ in the single-phase case. We consider an averaged system and prove that the Hamiltonian property is preserved under averaging. The single-phase solutions are written in terms of elliptic functions and, in the “focusing” case, Riemannian invariants are obtained for modulation equations. The characteristic rates of the averaged system are stated in terms of complete elliptic integrals and the self-similar solutions of the systemare obtained. Results of the corresponding simulations are given.     

Existence of maximal solutions for some very singular nonlinear fractional diffusion equations in 1D

We consider nonlinear parabolic equations involving fractional diffusion of the form \({\partial_t u + {(-\Delta)}^{s} \Phi(u)= 0,}\) with \({0 < s < 1}\), and solve an open problem concerning the existence of solutions for very singular nonlinearities \({\Phi}\) in power form, precisely \({\Phi'(u)=c\,u^{-(n+1)}}\) for some \({0 < n < 1}\). We also include the logarithmic diffusion equation \({\partial_t u + {(-\Delta)}^{s} \log(u)= 0}\), which appears as the case \({n=0}\). We consider the Cauchy problem with nonnegative and integrable data \({u_0(x)}\) in one space dimension, since the same problem in higher dimensions admits no nontrivial solutions according to recent results of the author and collaborators. The limit solutions we construct are unique, conserve mass, and are in fact maximal solutions of the problem. We also construct self-similar solutions of Barenblatt type, which are used as a cornerstone in the existence theory, and we prove that they are asymptotic attractors (as \({t\to\infty}\)) of the solutions with general integrable data. A new comparison principle is introduced.     

非线性四阶周期边值问题多个正解的存在性

利用不动点和度理论,证明了四阶周期边值问题u(4)(t)-βu″(t)+αu(t)=λf(t,u(t)),0≤t≤1,u(i)(0)=u(i)(1),i=0,1,2,3,至少存在两个正解,其中β>-2π2,0<α<(1/2β+2π2)2,α/π4+β/π2+1>0,f:[0,1]×[0,+∞)→[0,+∞)是连续函数,λ>0是常数.     

Stress distributions in highly frictional granular heaps

The practice of storing granular materials in stock piles occurs throughout the world in many industrial situations. As a result, there is much interest in predicting the stress distribution within a stock pile. In 1981, it was suggested from experimental work that the peak force at the base does not occur directly beneath the vertex of the pile, but at some intermediate point resulting in a ring of maximum pressure. With this in mind, any analytical solution pertaining to this problem has the potential to provide useful insight into this phenomenon. Here, we propose to utilize some recently determined exact parametric solutions of the governing equations for the continuum mechanical theory of granular materials for two and three-dimensional stock piles. These solutions are valid provided sin = 1, where is the angle of internal friction, and we term such materials as highly frictional. We note that there exists materials possessing angles of internal friction around 60 to 65 degrees, resulting in values of sin equal to around 0.87 to 0.91. Further, the exact solutions presented here are potentially the leading terms in a perturbation solution for granular materials for which 1- sin is close to zero. The model assumes that the stock pile is composed of two regions, namely an inner rigid region and an outer yield region. The exact parametric solution is applied to the outer yield region, and the solution is extended continuously into the inner rigid region. The results presented here extend previous work of the authors to the case of highly frictional granular solids.     

A wave equation with structural damping and nonlinear memory

In this paper, we obtain the critical exponent for a wave equation with structural damping and nonlinear memory: $$ u_{tt}-\triangle u + \mu\,(-\triangle)^{\frac12} u_t = \int\nolimits_0^t (t-s)^{-\gamma}\,|u(s,\cdot)|^p\,ds,$$ where μ > 0. In the supercritical case, we prove the existence of small data global solutions, whereas, in the subcritical case, we prove the nonexistence of global solutions for suitable arbitrarily small data, in the special case μ = 2.     

Enumerating solutions to

Let be polynomials with integer coefficients. This paper presents a fast method, using very little temporary storage, to find all small integers satisfying . Numerical results include all small solutions to ; all small solutions to ; and the smallest positive integer that can be written in ways as a sum of two coprime cubes.

     

Boussinesq方程组在Besov空间中局部解的存在性和延拓准则

本文研究二维无粘性Boussinesq方程组在超临界Besov空间B_(p,q)~s(R~2),s>1+2/p,1相似文献   

Classification of positive solutions to an integral system with the poly-harmonic extension operator

In this paper, we investigate the positive solutions to the following integral system with a polyharmonic extension operator on R~+_n:{u(x)=c_n,a∫_?R_+~n(x_n~(1-a_v)(y)/|x-y|~(n-a))dy,x∈R_+~n,v(y)=c_n,a∫_R_+~n(x_n~(1-a_uθ)(x)/|x-y|~(n-a))dx,y∈ ?R_+~n,where n 2, 2-n a 1, κ, θ 0. This integral system arises from the Euler-Lagrange equation corresponding to an integral inequality on the upper half space established by Chen(2014). The explicit formulations of positive solutions are obtained by the method of moving spheres for the critical case κ =n-2+a/n-a,θ =n+2-a/ n-2+a. Moreover,we also give the nonexistence of positive solutions in the subcritical case for the above system.     

Classification of minimal mass blow-up solutions for an $${L^{2}}$$ critical inhomogeneous NLS

We establish the classification of minimal mass blow-up solutions of the \({L^{2}}\) critical inhomogeneous nonlinear Schrödinger equation

$$i\partial_t u + \Delta u + |x|^{-b}|u|^{\frac{4-2b}{N}}u = 0,$$

thereby extending the celebrated result of Merle (Duke Math J 69(2):427–454, 1993) from the classic case \({b=0}\) to the case \({0< b< {\rm min} \{2,N\} }\), in any dimension \({N \geqslant 1}\).

     

Blowing up of solutions to the Cauchy problem for the generalized Zakharov system with combined power-type nonlinearities

This paper deals with blowing up of solutions to the Cauchy problem for a class of general- ized Zakharov system with combined power-type nonlinearities in two and three space dimensions. On the one hand, for c0 = +∞ we obtain two finite time blow-up results of solutions to the aforementioned system. One is obtained under the condition α≥ 0 and 1 + 4/N ≤ p N +2/N-2 or α 0 and 1 p 1 + 4/N (N = 2, 3); the other is established under the condition N = 3, 1 p N +2/N-2 and α(p-3) ≥ 0. On the other hand, for c0 +∞ and α(p-3) ≥ 0, we prove a blow-up result for solutions with negative energy to the Zakharov system under study.