Modeling Supply Networks and Business Cycles as Unstable Transport Phenomena

Physical concepts developed to describe instabilities in traffic flows can be generalized in a way that allows one to understand the well-known instability of supply chains (the so-called ``bullwhip effect''). That is, small variations in the consumption rate can cause large variations in the production rate of companies generating the requested product. Interestingly, the resulting oscillations have characteristic frequencies which are considerably lower than the variations in the consumption rate. This suggests that instabilities of supply chains may be the reason for the existence of business cycles. At the same time, we establish some link to queuing theory and between micro- and macroeconomics.Comment: For related work see http://www.helbing.or

Methods and Measures for Analyzing Complex Street Networks and Urban Form

Complex systems have been widely studied by social and natural scientists in terms of their dynamics and their structure. Scholars of cities and urban planning have incorporated complexity theories from qualitative and quantitative perspectives. From a structural standpoint, the urban form may be characterized by the morphological complexity of its circulation networks - particularly their density, resilience, centrality, and connectedness. This dissertation unpacks theories of nonlinearity and complex systems, then develops a framework for assessing the complexity of urban form and street networks. It introduces a new tool, OSMnx, to collect street network and other urban form data for anywhere in the world, then analyze and visualize them. Finally, it presents a large empirical study of 27,000 street networks, examining their metric and topological complexity relevant to urban design, transportation research, and the human experience of the built environment.Comment: PhD thesis (2017), City and Regional Planning, UC Berkele

The role of urban built heritage in qualify and quantify resilience. Specific issues in Mediterranean city

The Mediterranean city represents a significant example of urban organism, based on masonry construction and characterized by typological processes of growth. The material consistency and the temporal continuity of built heritage in Mediterranean city make relevant its interpretation and analysis according to the resilient approach. The declination of this approach in many disciplines generated a substantial diversity among the definitions of resilience (Francis and Bekera, 2014). Consequently, frameworks, adopted for a quantitative or qualitative assessment, underline the lack of standardization and rigor in defining resilience measurements. A review of resilience literature and actual applications in urban context permit to understand that there are different operators working on the field: on the one hand there are international organizations, on the other hand there are academics. The review of both the two ambits of investigation intends to clarify specific properties and convergence points in order to trace an evolution of conceptual framework and to identify general features of urban resilience. This process is fundamental in focusing the main aims of the research program: the definition of the role of urban built heritage, given by the close correlation between masonry constructive technique, typologies and morphologies, its material value in urban system, and its relevance in Mediterranean city in constitution of urban resilience (UNISDR, 2012a). Despite an increasing number of academic studies concerning the role of built environment in defining and improving cities resilience, their major attention is still focused on street patterns and lifelines infrastructures. The paper concludes how the role of built heritage remains insufficiently explored and a correct definition of urban structure is still missing inside the domain of infrastructural resilience