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51.
This article concerns the iteration of quasiregular mappings on \(\mathbb {R}^d\) and entire functions on \(\mathbb {C}\). It is shown that there are always points at which the iterates of a quasiregular map tend to infinity at a controlled rate. Moreover, an asymptotic rate of escape result is proved that is new even for transcendental entire functions. Let \(f:\mathbb {R}^d\rightarrow \mathbb {R}^d\) be quasiregular of transcendental type. Using novel methods of proof, we generalise results of Rippon and Stallard in complex dynamics to show that the Julia set of f contains points at which the iterates \(f^n\) tend to infinity arbitrarily slowly. We also prove that, for any large R, there is a point x with modulus approximately R such that the growth of \(|f^n(x)|\) is asymptotic to the iterated maximum modulus \(M^{n}(R,f)\). 相似文献
52.
本文针对国内高校尤其是工科院校学生培养中普遍存在的教学环节设置低年级专业渗透不够、高年级研究性不足的问题,提出开设贯穿于四年的工科学生培养专业研究实践教学模式。文章阐述了工科大学专业研究实验的研究性与专业化思想,在此基础上提出应根据学生在学习过程中所处的不同学习阶段有侧重的选择实验项目,以期帮助学生理解基础课程与专业课程之间的知识关联、形成统一的学科知识体系,满足后续工作、科研的需求的同时培养他们对于专业的感情。文章在此基础上,依据所提出的教学模式给出了相应的教学实验示例。旨在为应用工程类专业学生培养提供一种新的教学思路和教学模式,调动学生主观能动性的同时推进学研结合。 相似文献
53.
Shangqing Li Jinglong Ma Xiaojun Wu Baolong Zhang Chen Ouyang Tianze Wang Dan Wang Xuan Wang Yutong Li 《中国光学快报(英文版)》2021,(5):60-64
We propose a spatial diffraction diagnostic method via inserting a millimeter-gap double slit into the collimated terahertz beam to monitor the minute variation of the terahertz beam in strong-field terahertz sources, which is difficult to be resolved in conventional terahertz imaging systems. To verify the method, we intentionally fabricate tiny variations of the terahertz beam through tuning the iris for the infrared pumping beam before the tilted-pulse-front pumping setups.The phenomena can be well explained by the theory based on the tilted-pulse-front technique and terahertz diffraction. 相似文献
54.
A theorem of Maranda [1, Section 30] states that if F is a finitegroup, p is a prime and pe exactly divides |F|, then a ZpF-latticeM is determined up to isomorphism by its finite quotient M/pe+1M.If M is a free Zp-module of rank d, this is equivalent to sayingthat representations of F in GLd(Zp) are determined up to equivalenceby their images modulo pe+1. 1991 Mathematics Subject Classification20E18, 22E20. 相似文献
55.
56.
Dan Abramovich Tyler J. Jarvis 《Proceedings of the American Mathematical Society》2003,131(3):685-699
In this note we give a new, natural construction of a compactification of the stack of smooth -spin curves, which we call the stack of stable twisted -spin curves. This stack is identified with a special case of a stack of twisted stable maps of Abramovich and Vistoli. Realizations in terms of admissible -spaces and -line bundles are given as well. The infinitesimal structure of this stack is described in a relatively straightforward manner, similar to that of usual stable curves.
We construct representable morphisms from the stacks of stable twisted -spin curves to the stacks of stable -spin curves and show that they are isomorphisms. Many delicate features of -spin curves, including torsion free sheaves with power maps, arise as simple by-products of twisted spin curves. Various constructions, such as the -operator of Seeley and Singer and Witten's cohomology class go through without complications in the setting of twisted spin curves.
57.
Zhihang Peng Dongxu Yan Qiang Chen Deqiong Xin Dan Liu Dingquan Xiao Jianguo Zhu 《Current Applied Physics》2014,14(12):1861-1866
Aurivillius phase Bi3Ti1−xTaxNb1−xWxO12 high temperature piezoceramics were prepared by a conventional solid state reaction method. The crystal structure, dielectric, electrical conduction and piezoelectric properties were systematically studied. Pure or modified Bi3TiNbO9 ceramics revealed the presence of only two-layered Aurivillius phase, indicating that Ta/W doping entered into the B-site of pseudo-perovskite structure and formed solid solutions. The Curie temperature had a strong reliance on the structural distortion. Furthermore, Ta/W dopants act as a donor doping, decrease the number of oxygen vacancies and facilitate the domain wall motion. As a result, Ta/W modifications significantly increase the DC resistivity and piezoelectric properties. Bi3Ti0.98Ta0.02Nb0.98W0.02O12 ceramics possess the optimum d33 value (∼12.5 pC/N) together with a high TC point (∼893 °C). Moreover, the resonance–antiresonance spectra demonstrate that the Ta/W-BTN ceramics are indeed piezoelectric in nature at 600 °C. The d33 value of BTTNW-2 ceramic remains ∼12.2 pC/N after annealing at 700 °C. These factors suggest that the BTTNW-based ceramic is a promising candidate for ultra-high temperature sensor applications. 相似文献
58.
59.
60.
Dan Knopf 《Journal of Geometric Analysis》2009,19(4):817-846
Valuable models for immortal solutions of Ricci flow that collapse with bounded curvature come from locally $\mathcal{G}Valuable models for immortal solutions of Ricci flow that collapse with bounded curvature come from locally
G\mathcal{G}
-invariant solutions on bundles
GN\hookrightarrowM \oversetp? Bn\mathcal{G}^{N}\hookrightarrow\mathcal{M}\,\overset{\pi }{\mathcal{\longrightarrow}}\,\mathcal{B}^{n}
, with
G\mathcal{G}
a nilpotent Lie group. In this paper, we establish convergence and asymptotic stability, modulo smooth finite-dimensional
center manifolds, of certain ℝ
N
-invariant model solutions. In case N+n=3, our results are relevant to work of Lott classifying the asymptotic behavior of all 3-dimensional Ricci flow solutions
whose sectional curvatures and diameters are respectively
O(t-1)\mathcal{O}(t^{-1})
and
O(t1/2)\mathcal{O}(t^{1/2})
as t→∞. 相似文献