杂系统.pdf

系统科学 系统科学 与 复杂网络 与 复杂网络 狄增如 狄增如 北京师范大学管理学院系统科学系 北京师范大学管理学院系统科学系 北京师范大学复杂性研究中心 北京师范大学复杂性研究中心 2010.8 2010.8 Simple Complicated Complex System Complex Systems Complex Systems Complex systems are all around us: – economies – nature: ant, bee, bird colonies – little robots Complex systems Often-cited examples of complex systems in nature and society include the brain, the immune system, biological cells, metabolic networks, ant colonies, the Internet and World Wide Web, economic markets, and human socialnetworks. There is no generally accepted formal definition of “complex system”. Informally, a complex system is a large network of relatively simple components with no central control, in which emergent complex behavior is exhibited. 生物系统 社会经济系统 Complexity Research —— —— Understanding and Engineering Emergence Understanding and Engineering Emergence Complex systems have many autonomous units with adaptive capabilities, and show important emergent phenomena. One of the greatest challenges in building a science of such systems is precisely to understand – how it is that micro level properties determine or at least influence those on the macro level. Our current lack of understanding presents a huge obstacle in designing systems with specified behavior – to design the units of a system, their interactions and adaptive features, so as to achieve a targeted behavior from the whole. Complexity Approach Emergent properties: Local and simple interactions Global behavior