On the functional equation f(x+g(y))-f(y+g(y))=f(x)-f(y) on groups

We solve the equation

On the system of functional equationsf(x + y) = f(x) + f(y) andf(xy) = p (x)f(y) + q(y)f(x)

Aequationes mathematicae -     

The matrix equationa(x∘y)=a(x)+a(x)a(y)+a(y)

Aequationes mathematicae -     

The stability of RDDE\ddot x(t) + p_1 (t)\dot x(t) + q_1 (t)x(t) + p_2 (t)\dot x(t - r(t)) + q_2 (t)x(t - r(t)) = O

In this paper, the author considered the stability of zero solution of linear RDDE $$\begin{gathered} \ddot x(t) + p_1 (t)\dot x(t) + q_1 (t)x(t) + p_2 (t)\dot x(t - r(t)) + q_2 (t)x(t - r(t)) = O, \hfill \\ \ddot x(t) + p_1 (t)\dot x(t) + q_1 (t)x(t) + p_2 (t)\dot x(t - r(t)) = O \hfill \\ \end{gathered} $$ using Liapunov-Razumikhin functional and transformations and obtained some sufficient conditions for the stability of Eqs.(1) and (2). These results are suitable both for boundedp _i (t),q _i (t) andr(t).i=1,2.     

On the Diophantine system $$f(z)\,{=}\,f(x)f(y)\,{=}\,f(u) f(v)$$

We show that the Diophantine system

$$\begin{aligned} f(z)=f(x)f(y)=f(u)f(v) \end{aligned}$$

has infinitely many nontrivial positive integer solutions for \(f(X)=X^2-1\), and infinitely many nontrivial rational solutions for \(f(X)=X^2+b\) with nonzero integer b.

     

Gal(E/F)与Gal(L(E)/L(F))的同构

Let E be a field of finite extension of a perfect field F. We show that Gal(E/F) is isomorphic to Gal(L(E)/L(F)).     

关于数论函数方程φ(x_1…x_(n-1)x_n)=m(φ(x_1)+…+φ(x_(n-1))+φ(x_n))

运用Euler函数的性质证明了:当n>1时,方程φ(x_1…x_(n-1)x_n)=m(φ(x_1)+…+φ(x_(n-1))+φ(x_n))仅有有限多组正整数解(x_1,…,x_(n-1),x_n),得到了这些解都满足max{x_1,…,x_(n-1),x_n}≤2m⁴(n-1)4(n-1)²n2n².     

On the functional equation $$f(x+y)=f(x)+f(y)$$f(x+y)=f(x)+f(y)

Monatshefte für Mathematik - An extension of the linearity of the continuous solutions of the functional equation $$f(x+y)=f(x)+f(y)$$ to measurable functions is presented.     

Über die Funktionalgleichung f(f(x)*f(y))=f(x*y)

In this paper, the general solution of three functional equations occuring in interpolation theory are given in the general situation when variables belong to a semi-group with unit. We then specialize to some particular cases by specifying either the semi-group, or adding some regular properties like continuity or measurability.     

Radiation effects of poly(vinylidene fluoride) (PVDF) (I)

The relationship between the crystallinity of poly (vinylidene fluoride) (PVDF) and electron radiation effects is studied with differential scanning calorimeter and X-ray diffraction. The form of crystal of PVDF is not changed. In the low dose zone (lower than 400 kGy), the crystallinity of PVDF increases slightly with the increase of absorbed dose, and then decreases slowly, whereas the decrease of the crystallinity is accelerated with the increase of the absorbed dose in high dose zone. Gel and Sol properties of irradiated samples of PVDF are also studied with extraction of N, N-dimethyl formamide. In a low dose range, it fits Charlesby-Pinner formula very well; however, with the increase of the dose, it begins to deviate from this formula because of the obstruction of the crystalline region of PVDF.