一类可逆生化反应模型的定性分析

本文研究一类可逆生化反应的数学模型 :dxdt=a-( b+1 ) x+x2 y-cx3,dydt=bx-x2 y+cx3.应用微分方程定性理论 ,完整地解决了该系统极限环的存在性、唯一性和不存在性等问题 .     

On an Identity of Ramanujan

In this paper our aim is to determine all the solutions of the functional equation f(a + b + c) + f(b + c + d) + f(a - d) = f(a + b + d) + f(a + c + d) + f(b - c), where a, b, c, d Zsatisfy ad = bc. This equation is a generalization of one of the identities of Ramanujan. He found two solutions, f(x) = x2, and f(x) = x4. We prove that every solution of the equation can be written as a linear combination of 11 independent solutions.     

一类微分系统的极限环分布情况

用定性分析和数值判定方法,对一类微分系统x=y,y=x(l-bx2) (α-cx2)y(其中l＞0,b＞0,c≠0)的极限环分布情况进行了研究,得出该系统有3个极限环,并且给出了该系统所有极限环的分布情况.     

Inverse scattering for the nonlinear Schrödinger equation II. Reconstruction of the potential and the nonlinearity in the multidimensional case

We solve the inverse scattering problem for the nonlinear Schrödinger equation on :

We prove that the small-amplitude limit of the scattering operator uniquely determines . Our proof gives a method for the reconstruction of the potentials . The results of this paper extend our previous results for the problem on the line.

     

指数Diophantine方程(bn)~x+(2n)~y=((b+2)n)~z的例外解

设b是大于3的正奇数.运用初等方法讨论了方程(bn)^x+(2n)x+(2n)^y=((b+2)n)y=((b+2)n)^z适合(x,y,z)≠(1,1,1)的正整数解(x,y,z,n).证明了:i)对于任何给定的正整数N,存在无穷多个b可使该方程有满足min{x,y,z}≥N的正整数解(x,y,z,n);ii)对于任何给定的b,该方程仅有有限多组正整数解(x,y,z,n)满足y>z=x.     

Liénard方程极限环的存在唯一性定理

<正> 的极限环的存在唯一性问题[1,2],给出了定理1,此定理的一个推论即已包含了熟知的Lienard定理以及Levinson-Smith[3],Sansone[2],Barbalat[4],余澍祥[5]的存在唯一性定理.作为定理1推论的直接应用,还对方程     

單調接近的半稳定的極限環線

<正> H.Poincare在其研究常微分方程dx/X(x,y)=dy/Y(x,y)(1)的經典工作中引入了許多極重要的概念,極限環線即其中之一,由於工程上的需要,在研究Van der Pol方程及其他問題上,極限環線的研究得到廣泛與深入的發展.例如可參考S.Lefschetz.     

Logistic型方程周期解和概周期解的存在性

In this paper, we study the Logistic type equation x= a（t）x -b（t）x^2＋ e（t）. Under the assumptions that e（t） is small enough and a（t）, b（t） are contained in some positive intervals, we prove that this equation has a positive bounded solution which is stable. Moreover, this solution is a periodic solution if a（t）, b（t） and e（t） are periodic functions, and this solution is an almost periodic solution if a（t）, b（t） and e（t） are almost periodic functions.     

Unb ounded Motions in Asymmetric Oscillators Dep ending on Derivatives

In this paper, we consider the unboundedness of solutions for the asymmetric equation x00+ax+?bx?+?(x)ψ(x0)+f(x)+g(x0)=p(t), where x+ = max{x, 0}, x? = max{?x, 0}, a and b are two different positive constants, f (x) is locally Lipschitz continuous and bounded,?(x), ψ(x), g(x) and p(t) are continuous functions, p(t) is a 2π-periodic function. We discuss the existence of unbounded solutions under two classes of conditions: the resonance case √1a+ √1b ∈Q and the nonresonance case√1a + √1b /∈Q.     

Estimate for the amplitude of the limit cycle of the Liénard equation

We consider the nonlinear Liénard equation \(\ddot x\left( t \right) + f\left( x \right)\dot x\left( t \right) + g\left( x \right) = 0\). Liénard obtained sufficient conditions on the functions f(x) and g(x) under which this equation has a unique stable limit cycle. Under additional conditions, we prove a theorem that permits one to estimate the amplitude (the maximum value of x) of this limit cycle from above. The theorem is used to estimate the amplitude of the limit cycle of the van der Pol equation \(\ddot x\left( t \right) + \mu \left[ {{x^2}\left( t \right) - 1} \right]\dot x\left( t \right) + x\left( t \right) = 0\).     

A remark on Jeśmanowicz’ conjecture for the non-coprimality case

Let a, b, c be relatively prime positive integers such that a² + b² = c². Je?manowicz' conjecture on Pythagorean numbers states that for any positive integer N, the Diophantine equation (aN)^x + (bN)^y = (cN)^z has no positive solution (x, y, z) other than x = y = z = 2. In this paper, we prove this conjecture for the case that a or b is a power of 2.     

测度链上非线性微分方程的三正解

运用文[1]中的Leggett—Williams不动点定理，我们给出了测度链上的非线性微分方程-x^△△(t)=f(t,x(σ(t))),t∈[a,b,]关于两点边值条件ax(a)-βx^△(a)=0，γx(σ(b)) δx^△(σ(b))=0三正解存在性准则。     

关于二次微分系统Ⅰ类方程的极限环之二

本文研究了二次微分系统Ⅰ类方程dx／dt=-y＋δx＋lx2＋mxy＋ny2,dy／dt=x的极限环问题,得到了当lι≠0时大范围内存在极限环的条件．     

Blow Up in a Semilinear Wave Equation

We consider a semilinear wave equation of the form u_tt(x, t) - Δu(x, t) = - m(x, t)u_t(x, t) + ∇Φ(x) ⋅ ∇u(x, t ) + b(x)|u(x, t)|^{p-2}u(x, t) where p > 2. We show, under suitable conditions on m, Φ, b, that weak solutions break down in finite time if the initial energy is negative. This result improves an earlier one by the author [1].     

Diophantine方程（a^m-1）（6^n-1）=x^2的一点注记

设a,b是适合min（a,b）〉1,2｜a,2＋b以及v（6—1）是正奇数,其中v（b-1）表示整除b-1的2的最高次数．本文运用初等方法以及同余性质,研究了方程（a^m-1）（b^n-1）=x^2的可解性．对某些特殊素数P,证明了该方程无解．证明了如果存在适合P≡±E3（mod8）的奇素数P,可使a≡-1（modP）...     

Lienard方程周期解、概周期解的存在性

本文考虑 Lienard方程 x″+f (x) x′+g(x) =e(t) ,我们得到 :当 -∞ 0且 0 相似文献   

平面2n+1次系统极限环的唯一性

讨论了微分方程组 dx/dt=-y(1 -ax2 n) +bx-cx2 n+ 1,dy/dt=x(1 -ax2 n) ,并且给出了其极限环存在唯一的条件 .     

ON THE UPPER ESTIMATES OF FUNDAMENTAL SOLUTIONS OF PARABOLIC EQUATIONS ON RIEMANNIAN MANIFOLDS

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Relative entropy maximization and directed diffusion equations

Motivated by the concept of maximum entropy methods in signal and image processing, we introduce and discuss a class of ‘directed diffusion equations’ with suitable boundary conditions. The paradigmatic ‘directed diffusion equation’ is The relative entropy $ Sb[f](t): = - \int_\Omega {f(t,x)} \;\ln \;(f(t,x)/b(x))dx $ is rapidly increasing along solution trajectories of (i). This suggests that solving (i) will yield efficient procedures for entropy maximization. We also discuss the asymptotic behavior of solutions of (i)—this is readily done because (i) has a large family of Ljapunov functionals.     

R~N空间中退化的logistic型拟线性椭圆方程正解存在唯一性

本文研究下列退化的logistic型p-Laplacian方程:-△Apu=a(x)|u|p-2u- b(x)|u|q-1u,x∈RN(N≥2)．在对系数a(x),b(x)在无穷远处的性质加以一般限制,得出了正解唯一存在性定理．我们的结果改进了文[1]和[2]中的相应结果．