Peut-on estimer la singularité des villes (post-)soviétiques ? = How to estimate the singularity of (post-)Soviet cities?

Bien que l’urbanisation de l’ex-URSS représente une expérience historique unique, cet article questionne la possibilité de distinguer la part des processus généraux de croissance des villes, de leur localisation et de leur spécialisation, de la part des processus particuliers liés à la taille et à l’organisation politique du territoire et de la part des processus singuliers ne pouvant s’expliquer en dehors de la connaissance des événements ayant affecté les villes analysées. En recourant à plusieurs niveaux et différents types de modèles, nous identifions le résidu (ce qui « résiste à la modélisation ») aux évolutions singulières à l’Union soviétique et à l’histoire locale des villes. Pour cela, nous avons produit une base de données urbaines harmonisées et ajusté des modèles hiérarchiques, spatiaux et statistiques à ces données historiques pour conclure à une hiérarchisation relativement banale des villes soviétiques, une distribution spatiale de pays vastes (accentuée par l’extraction de ressources du sous-sol) et des trajectoires singulières. / Although the urbanisation of the Former Soviet Union is a unique experience, this article questions the possibility of estimating the share of the generic processes of urban growth, spatial location and economic specialisation, the share of the particular processes of urbanisation linked to the size and political organisation of the country, and the share of the singular processes that cannot be explained without a local knowledge of the events which happened in the cities under study. Using several types of models at different scales, we identify the residual as the element that “resists modelling” and illustrates the singular evolutions of the Soviet Union and its cities. To do so, we built a harmonised urban database and fitted hierarchical, spatial and regression models. We conclude that city size inequality increased in a generic manner compared to other systems of cities, that the spatial distribution of cities resemble that of vast countries (especially with the increased reliance on sub-surface resources), and that there exists a set of singular urban trajectories

MetaZipf. A dynamic meta-analysis of city size distributions

The results from urban scaling in recent years have held the promise of increased efficiency to the societies who could actively control the distribution of their cities’ size. However, little evidence exists as to the factors which influence the level of urban unevenness, as expressed by the slope of the rank-size distribution, partly because the diversity of results found in the literature follows the heterogeneity of analysis specifications. In this study, I set up a meta-analysis of Zipf’s law which accounts for technical as well as topical factors of variations of Zipf’s coefficient. I found 86 studies publishing at least one empirical estimation of this coefficient and recorded their metadata into an open database. I regressed the 1962 corresponding estimates with variables describing the study and the estimation process as well as socio-demographic variables describing the territory under enquiry. A dynamic meta-analysis was also performed to look for factors of evolution of city size unevenness. The results of the most interesting models are presented in the article, whereas all analyses can be reproduced on a dedicated online platform. The results show that on average, 40% of the variation of Zipf’s coefficients is due to the technical choices. The main other variables associated with distinct evolutions are linked to the urbanisation process rather than the process of economic development and population growth. Finally, no evidence was found to support the effectiveness of past planning actions in modifying this urban feature

Diverse cities or the systematic paradox of Urban Scaling Laws

Scaling laws are powerful summaries of the variations of urban attributes with city size. However, the validity of their universal meaning for cities is hampered by the observation that different scaling regimes can be encountered for the same territory, time and attribute, depending on the criteria used to delineate cities. The aim of this paper is to present new insights concerning this variation, coupled with a sensitivity analysis of urban scaling in France, for several socio-economic and infrastructural attributes from data collected exhaustively at the local level. The sensitivity analysis considers different aggregations of local units for which data are given by the Population Census. We produce a large variety of definitions of cities (approximatively 5000) by aggregating local Census units corresponding to the systematic combination of three definitional criteria: density, commuting flows and population cutoffs. We then measure the magnitude of scaling estimations and their sensitivity to city definitions for several urban indicators, showing for example that simple population cutoffs impact dramatically on the results obtained for a given system and attribute. Variations are interpreted with respect to the meaning of the attributes (socio-economic descriptors as well as infrastructure) and the urban definitions used (understood as the combination of the three criteria). Because of the Modifiable Areal Unit Problem (MAUP) and of the heterogeneous morphologies and social landscapes in the cities' internal space, scaling estimations are subject to large variations, distorting many of the conclusions on which generative models are based. We conclude that examining scaling variations might be an opportunity to understand better the inner composition of cities with regard to their size, i.e. to link the scales of the city-system with the system of cities

Mobile phone indicators and their relation to the socioeconomic organisation of cities

Thanks to the use of geolocated big data in computational social science research, the spatial and temporal heterogeneity of human activities is increasingly being revealed. Paired with smaller and more traditional data, this opens new ways of understanding how people act and move, and how these movements crystallise into the structural patterns observed by censuses. In this article we explore the convergence between mobile phone data and more traditional socioeconomic data from the national census in French cities. We extract mobile phone indicators from six months worth of Call Detail Records (CDR) data, while census and administrative data are used to characterize the socioeconomic organisation of French cities. We address various definitions of cities and investigate how they impact the statistical relationships between mobile phone indicators, such as the number of calls or the entropy of visited cell towers, and measures of economic organisation based on census data, such as the level of deprivation, inequality and segregation. Our findings show that some mobile phone indicators relate significantly with different socioeconomic organisation of cities. However, we show that relations are sensitive to the way cities are defined and delineated. In several cases, changing the city delineation rule can change the significance and even the sign of the correlation. In general, cities delineated in a restricted way (central cores only) exhibit traces of human activity which are less related to their socioeconomic organisation than cities delineated as metropolitan areas and dispersed urban regions

Empowering open science with reflexive and spatialised indicators

Bibliometrics have become commonplace and widely used by authors and journals to monitor, to evaluate and to identify their readership in an ever-increasingly publishing scientific world. This contribution introduces a multi-method corpus analysis tool, specifically conceived for scientific corpuses with spatialised content. We propose a dedicated interactive application that integrates three strategies for building semantic networks, using keywords (self-declared themes), citations (areas of research using the papers) and full-texts (themes derived from the words used in writing). The networks can be studied with respect to their temporal evolution as well as to their spatial expressions, by considering the countries studied in the papers under inquiry. The tool is applied as a proof-of-concept on the papers published in the online open access geography journal Cybergeo since its creation in 1996. Finally, we compare the three methods and conclude that their complementarity can help go beyond simple statistics to better understand the epistemological evolution of a scientific community and the readership target of the journal. Our tool can be applied by any journal on its own corpus, fostering thus open science and reflexivity

Defining urban clusters to detect agglomeration economies

Agglomeration economies are a persistent subject of debate in regional science and city planning. Their definition turns on whether or not larger cities are more efficient than smaller ones. Here, we complement existing discussions on agglomeration economies by providing a sensitivity analysis of estimated externalities to the definitions of urban agglomeration. We regress wages versus population and jobs over thousands of different definitions of cities in France, based on an algorithmic aggregation of spatial units. We also search for evidence of larger inequalities in larger cities. This paper therefore focuses on the spatial and economic complexity of the mechanisms defining agglomeration within and between cities

QUANTIFICATION OF ACCELERATED WEAR FOR ROAD MATERIALS BY USING A NEW TESTING APPARATUS

ABSTRACT This paper focuses on problem of loss aggregates on the surface layer of pavements in particular sites such as approaches to roundabouts and pedestrian crossings. Obtaining a long life-wearing course requires more than can be achieved by improving the properties of the wearing course in it. Generally, the traffic loads, temperature variations, the intrusion of water and freeze-thaw cycles, which will reduce the life of the wearing course, regardless of how well it is designed and constructed. The wearing course is an important interdependent component of the whole pavement. A durable and faultless wearing course acts to protect the base layers against the intrusion of water from above, which is essential to maintain its strength and serviceable life. The objective of this study is to evaluate the wear of a controlled set of pavements with various aggregate mixtures. A single parameter is not enough to describe the mechanisms of surface damage but we propose relationships between the constituents used in pavements and loss of aggregates

Unveiling relationships between crime and property in England and Wales via density scale-adjusted metrics and network tools

Scale-adjusted metrics (SAMs) are a significant achievement of the urban scaling hypothesis. SAMs remove the inherent biases of per capita measures computed in the absence of isometric allometries. However, this approach is limited to urban areas, while a large portion of the world’s population still lives outside cities and rural areas dominate land use worldwide. Here, we extend the concept of SAMs to population density scale-adjusted metrics (DSAMs) to reveal relationships among different types of crime and property metrics. Our approach allows all human environments to be considered, avoids problems in the definition of urban areas, and accounts for the heterogeneity of population distributions within urban regions. By combining DSAMs, cross-correlation, and complex network analysis, we find that crime and property types have intricate and hierarchically organized relationships leading to some striking conclusions. Drugs and burglary had uncorrelated DSAMs and, to the extent property transaction values are indicators of affluence, twelve out of fourteen crime metrics showed no evidence of specifically targeting affluence. Burglary and robbery were the most connected in our network analysis and the modular structures suggest an alternative to "zero-tolerance" policies by unveiling the crime and/or property types most likely to affect each other