Let P and AC be two primary sequences with min{P, AC} RLR<sup>∞</sup>,ρ(P) and p(AC) be the eigenvalues of P and AC, respectively. Let f ∈ C<sup>0</sup>(I, I) be a unimodal expanding m...Let P and AC be two primary sequences with min{P, AC} RLR<sup>∞</sup>,ρ(P) and p(AC) be the eigenvalues of P and AC, respectively. Let f ∈ C<sup>0</sup>(I, I) be a unimodal expanding map with expanding constant λ and m be a nonegative integer. It is proved that f has the kneading sequence K(f) (RC)<sup>*m</sup> * P if λ (ρ(P))<sup>1/2<sup>m</sup></sup>, and K(f)】(RC)<sup>*m</sup> * AC * E for any shift maximal sequence E if λ】(ρ(AC))<sup>1/2<sup>m</sup></sup>. The value of (ρ(P))<sup>1/2<sup>m</sup></sup> or (ρ(AC))<sup>1/2<sup>m</sup></sup> is the best possible in the sense that the related conclusion may not be true if it is replaced by any smaller one.展开更多
基金Project supported by the National Natural Science Foundation of China
文摘Let P and AC be two primary sequences with min{P, AC} RLR<sup>∞</sup>,ρ(P) and p(AC) be the eigenvalues of P and AC, respectively. Let f ∈ C<sup>0</sup>(I, I) be a unimodal expanding map with expanding constant λ and m be a nonegative integer. It is proved that f has the kneading sequence K(f) (RC)<sup>*m</sup> * P if λ (ρ(P))<sup>1/2<sup>m</sup></sup>, and K(f)】(RC)<sup>*m</sup> * AC * E for any shift maximal sequence E if λ】(ρ(AC))<sup>1/2<sup>m</sup></sup>. The value of (ρ(P))<sup>1/2<sup>m</sup></sup> or (ρ(AC))<sup>1/2<sup>m</sup></sup> is the best possible in the sense that the related conclusion may not be true if it is replaced by any smaller one.
文摘多功能饲草揉丝机在实际应用中存在容易堵塞以及抛扔距离不满足使用要求等问题,这些问题均与机内物料-气流耦合运动特性有关。为了探究揉丝机内物料与气流耦合运动规律,采用计算流体力学(Computational fluid dynamics,CFD)以及离散元(Discrete element method,DEM)耦合方法,建立物料揉丝过程中气流与散碎物料耦合作用模型,并对物料与气流之间的耦合运动规律进行数值模拟,通过气流速度测试与物料抛扔距离试验验证耦合模型与数值计算的准确性。研究表明:出料口4个测点的气流速度仿真值与实测值相对误差均在8.1%以内;额定转速范围内3种转速下物料平均抛扔距离数值计算结果与实测值相对误差均小于5%,验证了物料-气流耦合模型与数值计算结果的准确性。饲草物料破碎后沿着揉碎室内壁面做环流运动,并沿着出料管远离进料口一侧被抛出机外。揉丝机稳定运转后室内颗粒运动的最大速度始终在某一平均速度上下波动,速度均值体现了物料颗粒在锤片打击力作用下获得动能的大小。颗粒物料获得动能越大,装置越不易堵塞,物料的平均抛扔距离越远。研究结果可为揉丝机内物料-气流耦合运动特性优化、避免堵塞以及增加物料抛扔距离提供基础依据。