158 research outputs found
Modeling urbanization patterns with generative adversarial networks
In this study we propose a new method to simulate hyper-realistic urban
patterns using Generative Adversarial Networks trained with a global urban
land-use inventory. We generated a synthetic urban "universe" that
qualitatively reproduces the complex spatial organization observed in global
urban patterns, while being able to quantitatively recover certain key
high-level urban spatial metrics.Comment: 4 pages, 4 figure
Multiplex networks in metropolitan areas: generic features and local effects
Most large cities are spanned by more than one transportation system. These
different modes of transport have usually been studied separately: it is
however important to understand the impact on urban systems of the coupling
between them and we report in this paper an empirical analysis of the coupling
between the street network and the subway for the two large metropolitan areas
of London and New York. We observe a similar behaviour for network quantities
related to quickest paths suggesting the existence of generic mechanisms
operating beyond the local peculiarities of the specific cities studied. An
analysis of the betweenness centrality distribution shows that the introduction
of underground networks operate as a decentralising force creating congestions
in places located at the end of underground lines. Also, we find that
increasing the speed of subways is not always beneficial and may lead to
unwanted uneven spatial distributions of accessibility. In fact, for London --
but not for New York -- there is an optimal subway speed in terms of global
congestion. These results show that it is crucial to consider the full,
multimodal, multi-layer network aspects of transportation systems in order to
understand the behaviour of cities and to avoid possible negative side-effects
of urban planning decisions.Comment: 12 pages, 8 figures. Final version with an additional discussion on
the total congestio
The simplicity of planar networks
Shortest paths are not always simple. In planar networks, they can be very
different from those with the smallest number of turns - the simplest paths.
The statistical comparison of the lengths of the shortest and simplest paths
provides a non trivial and non local information about the spatial organization
of these graphs. We define the simplicity index as the average ratio of these
lengths and the simplicity profile characterizes the simplicity at different
scales. We measure these metrics on artificial (roads, highways, railways) and
natural networks (leaves, slime mould, insect wings) and show that there are
fundamental differences in the organization of urban and biological systems,
related to their function, navigation or distribution: straight lines are
organized hierarchically in biological cases, and have random lengths and
locations in urban systems. In the case of time evolving networks, the
simplicity is able to reveal important structural changes during their
evolution.Comment: 8 pages, 4 figure
Mapping road network communities for guiding disease surveillance and control strategies
Human mobility is increasing in its volume, speed and reach, leading to the
movement and introduction of pathogens through infected travelers. An
understanding of how areas are connected, the strength of these connections and
how this translates into disease spread is valuable for planning surveillance
and designing control and elimination strategies. While analyses have been
undertaken to identify and map connectivity in global air, shipping and
migration networks, such analyses have yet to be undertaken on the road
networks that carry the vast majority of travellers in low and middle income
settings. Here we present methods for identifying road connectivity
communities, as well as mapping bridge areas between communities and key
linkage routes. We apply these to Africa, and show how many highly-connected
communities straddle national borders and when integrating malaria prevalence
and population data as an example, the communities change, highlighting regions
most strongly connected to areas of high burden. The approaches and results
presented provide a flexible tool for supporting the design of disease
surveillance and control strategies through mapping areas of high connectivity
that form coherent units of intervention and key link routes between
communities for targeting surveillance.Comment: 11 pages, 5 figures, research pape
Urbanization and Economic Complexity
Urbanization plays a crucial role in the economic development of every
country. The mutual relationship between the urbanization of any country and
its economic productive structure is far from being understood. We analyzed the
historical evolution of product exports for all countries using the World Trade
Web (WTW) with respect to patterns of urbanization from 1995-2010. Using the
evolving framework of economic complexity, we reveal that a country's economic
development in terms of its production and export of goods, is interwoven with
the urbanization process during the early stages of its economic development
and growth. Meanwhile in urbanized countries, the reciprocal relation between
economic growth and urbanization fades away with respect to its later stages,
becoming negligible for countries highly dependent on the export of resources
where urbanization is not linked to any structural economic transformation.Comment: 11 Pages, 5 Figure
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