Normalized solutions for a fourth-order Schr{o}dinger equation with positive second-order dispersion coefficient

We are concerned with the existence and asymptotic properties of solutions to the following fourth-order Schr{o}dinger equation begin{equation}label{1} {Delta}^{2}u+mu Delta u-{lambda}u={|u|}^{p-2}u, ~~~~x in R^{N} end{equation} under the normalized constraint $$int_{{mathbb{R}^N}} {{u}^2}=a^2,$$ where $N!geq!2$, $a,mu!>!0$, $2+frac{8}{N}!<!p!<! 4^{*}!=!frac{2N}{(N-4)^{+}}$ and $lambdainR$ appears as a Lagrange multiplier. Since the second-order dispersion term affects the structure of the corresponding energy functional $$ E_{mu}(u)=frac{1}{2}{||Delta u||}_2^2-frac{mu}{2}{|| abla u||}_2^2-frac{1}{p}{||u||}_p^p $$ we could find at least two normalized solutions to (ref{1}) if $2!+!frac{8}{N}!<! p!<!{ 4^{*} }$ and $mu^{pgamma_p-2}a^{p-2}!<!C$ for some explicit constant $C!=!C(N,p)!>!0$ and $gamma_p!=!frac{N(p!-!2)}{4p}$. Furthermore, we give some asymptotic properties of the normalized solutions to (ref{1}) as $muto0^+$ and $ato0^+$, respectively. In conclusion, we mainly extend the results in cite{DBon,dbJB}, which deal with (ref{1}), from $muleq0$ to the case of $mu>0$, and also extend the results in cite{TJLu,Nbal}, which deal with (ref{1}), from $L^2$-subcritical and $L^2$-critical setting to $L^2$-supercritical setting.