林兹第五版:计算机科学入门 - 形式语言与自动机

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《形式语言与自动机:第五版》是由彼得·林兹所著的一本经典教材,专为计算机科学和计算机工程专业的二年级和三年级学生设计,旨在介绍形式语言、自动机、计算理论等核心概念。这门课程在计算机科学的教学大纲中占据着重要地位,因为它为学生们提供了早期接触理论计算的基础。 本书覆盖了形式语言理论的各个方面,包括语言的定义、构造、性质和分类,以及自动机(如确定型自动机、非确定型自动机、有限自动机、无限自动机等)的工作原理和应用。形式语言是描述符号序列的规则集合,而自动机则是用来识别这些语言的机器模型,它们在计算机科学中扮演着理解输入数据结构和执行决策的关键角色。 书中探讨了如何通过构造正规表达式来描述特定的语言,以及如何使用图灵机等抽象模型来衡量一个系统的计算能力。此外,读者还将学习如何将实际问题转化为形式语言和自动机的问题,以便于设计算法和构建计算机程序。 本书采用清晰易懂的方式阐述复杂的理论概念,配以丰富的例题和练习,帮助学生逐步掌握理论并将其应用到实践中。通过阅读和学习本书,学生不仅能够建立起坚实的理论基础,而且还能培养解决问题的逻辑思维和抽象建模能力,这对于后续的软件开发、系统分析和理论研究都至关重要。 总结来说,《形式语言与自动机:第五版》是一本深入浅出的教材,适合对计算机科学有兴趣的学生深入理解形式化的抽象思维,以及那些希望在自动机理论和计算复杂性等领域进一步探索的专业人士。无论是在课堂学习还是自我研读中,它都是一个不可或缺的参考资料。

For macroscopically anisotropic media in which the variations in the phase stiffness tensor are small, formal solutions to the boundary-value problem have been developed in the form of perturbation series (Dederichs and Zeller, 1973; Gubernatis and Krumhansl, 1975 ; Willis, 1981). Due to the nature of the integral operator, one must contend with conditionally convergent integrals. One approach to this problem is to carry out a “renormalization” procedure which amounts to identifying physically what the conditionally convergent terms ought to contribute and replacing them by convergent terms that make this contribution (McCoy, 1979). For the special case of macroscopically isotropic media, the first few terms of this perturbation expansion have been explicitly given in terms of certain statistical correlation functions for both three-dimensional media (Beran and Molyneux, 1966 ; Milton and Phan-Thien, 1982) and two-dimensional media (Silnutzer, 1972 ; Milton, 1982). A drawback of all of these classical perturbation expansions is that they are only valid for media in which the moduli of the phases are nearly the same, albeit applicable for arbitrary volume fractions. In this paper we develop new, exact perturbation expansions for the effective stiffness tensor of macroscopically anisotropic composite media consisting of two isotropic phases by introducing an integral equation for the so-called “cavity” strain field. The expansions are not formal but rather the nth-order tensor coefficients are given explicitly in terms of integrals over products of certain tensor fields and a determinant involving n-point statistical correlation functions that render the integrals absolutely convergent in the infinite-volume limit. Thus, no renormalization analysis is required because the procedure used to solve the integral equation systematically leads to absolutely convergent integrals. Another useful feature of the expansions is that they converge rapidly for a class of dispersions for all volume fractions, even when the phase moduli differ significantly.

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