References of "Thomas, Isabelle"
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See detailCity delineation in European applications of LUTI models: review and tests
Thomas, Isabelle; Jones, Jonathan; Caruso, Geoffrey UL et al

in Transport Reviews (2018), 38(1), 6-32

This paper stresses the lack of attention paid to the geographical definitions of cities in LUTI models as one key detrimental aspect to transferring and generalising LUTI results. First, the ... [more ▼]

This paper stresses the lack of attention paid to the geographical definitions of cities in LUTI models as one key detrimental aspect to transferring and generalising LUTI results. First, the argumentation develops from a meta-analysis of peer-reviewed publications about LUTI applications in European cities. We show that most authors do not assess findings against potential geographical biases. Second, theoretical simulations are conducted with UrbanSim applied to a synthetic urban area. By varying the geographical limits of the system and population endowments, our simulations confirm that the absence of control on city delineation weakens the results. Finally, the paper suggests methodological guidelines to improve the comparability of LUTI applications and push forward their theoretical agenda. [less ▲]

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See detailMeasuring urban forms from inter-building distances: Combining MST graphs with a Local Index of Spatial Association
Caruso, Geoffrey UL; Hilal, Mohamed; Thomas, Isabelle

in Landscape & Urban Planning (2017), 163

A new method is proposed for characterising local urban patterns at the scale of a large urban region. The approach overcomes the difficulties of surface-based representations of built-up morphologies and ... [more ▼]

A new method is proposed for characterising local urban patterns at the scale of a large urban region. The approach overcomes the difficulties of surface-based representations of built-up morphologies and provides an efficient way to account for the proximity of built and non-built land. The strength of the approach resides in the direct use of the coordinates of each building, a very parsimonious input of external parameters, and a local spatial statistical perspective. The method consists in, first, constructing and clumping the Minimum Spanning Tree (MST) that links each building to its neighbours in order to obtain connected urban and suburban graph subsets, and second, measuring a Local Index of Spatial Association (LISA) on inter-building distances in order to characterise patterns. The method differentiates heterogeneous settlements from statistically significant homogeneous clusters with either long or short connections between buildings. The method is applied to the Southern periphery of Brussels (Belgium). [less ▲]

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See detailBicycle sharing system ‘success’ determinants
Médard de Chardon, Cyrille UL; Caruso, Geoffrey UL; Thomas, Isabelle

in Transportation Research. Part A : Policy & Practice (2017), 100

Many municipalities assert bicycle sharing systems (BSS) as having many benefits, justifying their adoption, yet few explicitly state the purpose of their system making comparison or determination of ... [more ▼]

Many municipalities assert bicycle sharing systems (BSS) as having many benefits, justifying their adoption, yet few explicitly state the purpose of their system making comparison or determination of success impossible. In addition, the apprehension of many BSS operators to share data further hinders comparison. This paper estimates the number of daily trips from publicly available data for 75 BSS case studies across the world and provides trips per bike per day scores as a comparison of performance and success. Results reveal that a third of case studies have fewer than the psychologically important one trip per bicycle per day. To ascertain what factors are associated with this metric we estimate models with independent variables related to system attributes, station density, weather, geography and transportation infrastructure. Our analysis provides strong evidence undermining the ‘network effect’ promoted by influential BSS policy makers that expanding system size increases performance. Finally our results describe and discuss causal variables associated with higher BSS performance. [less ▲]

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See detailBike-share rebalancing strategies, patterns, and purpose
Medard de Chardon, Cyrille UL; Caruso, Geoffrey UL; Thomas, Isabelle

in Journal of Transport Geography (2016), 55

We provide a first spatio-temporal exploration of bicycle sharing system (BSS) rebalancing patterns from data extracted for individual stations at a fine temporal scale and operator interviews. Analyzing ... [more ▼]

We provide a first spatio-temporal exploration of bicycle sharing system (BSS) rebalancing patterns from data extracted for individual stations at a fine temporal scale and operator interviews. Analyzing rebalancing operations for nine BSS, we describe implications for operators, municipalities, and future optimization work. We find that stations adjacent to transit hubs receive disproportionate amounts of rebalancing relative to trips and that rebalancing is more often responding to morning and afternoon demand exceeding station dock capacities rather than longer term accumulations of bicycles. More importantly, we observe some operator’ rebalancing behaviors constrained between opposing goals of maximizing trips, profits, and service level agreements. Many BSS have no explicitly defined purpose, but existing rebalancing strategies can support or clash with the purpose or suggested benefits of a BSS. [less ▲]

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See detailGreener and larger neighbourhoods make cities more sustainable! A 2D urban economics perspective
Caruso, Geoffrey UL; Cavailhès, Jean; Peeters, Dominique et al

in Computers, Environment & Urban Systems (2015), 54

We analyse urban growth forms by means of a 2D microeconomic model where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow more densely when households ... [more ▼]

We analyse urban growth forms by means of a 2D microeconomic model where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow more densely when households have the possibility to enlarge the neighbourhood in which they value green space, thus emphasizing the importance of neighbourhood planning in particular for facilitating short trips and views of green amenities. We also show by simulation that the size and form of the city, relative to the size and form of neighbourhoods, impact on the decision of households to leapfrog land or not, thus impacting on the emergence of scattered urbanisation patterns. We conclude that carefully addressing the spatial arrangement of green space and buildings and facilitating trips within neighbourhood units constitute an effective policy lever and an attractive way to deliver more sustainable cities. We further argue that our theoretical experiment with complementary analytical and computer-based simulation provides micro-economic reasoning to the main elements of the Garden City and neighbourhood unit planning concepts. [less ▲]

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See detailMonocentric urban simulation models: getting closer to fractal properties and landscape representation
Caruso, Geoffrey UL; Frankhauser, Pierre; Vuidel, Gilles et al

Scientific Conference (2015, November)

Urban growth generates spatial patterns that in many cases demonstrate fractal properties. Geocomputational models, particularly cellular automata and spatial agent-based simulation models have been used ... [more ▼]

Urban growth generates spatial patterns that in many cases demonstrate fractal properties. Geocomputational models, particularly cellular automata and spatial agent-based simulation models have been used over the last 20 years to generate urbanisation patterns with the aim to replicate at best observed expansion footprints, including matching observed and simulated fractal dimensions. In applied cases, with the addition of constraints at multiple scales (land constraints, threshold per zones, etc.) simulation models seem to perform rather well and obtain sound urban fractal dimensions. Models that are more parsimonious in parameters however do not seem to perform as well. Exceptions are those models directly inspired from physics such as DLA (Diffusion Limited Aggregation) or DBM (Dielectric Breakdown Models) but these are frustrating when it comes to behavioural or economic interpretation. Models with explicit micro-economic component in a monocentric setting also seem to lag behind in terms of fractal performance: unless exogenous spatial heterogeneity is provided, the spatial outcome of these models is too homogenous to resemble real cities, despite agglomeration and dispersion processes at neighbourhood scale and despite the self-emergence of road networks and subsequent open land lock-ins. Rather than resolving to exogenous polycentric setting or exogenous stochasticity that would provide better looking outcomes, we investigate this insatisfaction by exploring the results of an augmented micro-economic simulation model on a theoretical monocentric space. The innovations are brought along three rationales: Firstly, an assumption is made that the length of the infrastructure network should feed back into households budget. Cities cannot expand too quickly not only because of unitary commuting costs but also infrastructure costs. We therefore implement an infrastructure tax that should lead to agglomeration or a more efficient generation of roads from the city perspective. Secondly, we assume that the infill of undeveloped spaces by new residents is limited by residents who settled earlier in the city and refuse important utility losses in terms of open green space. This leads to relaxing the assumption of a dynamic adaptation of rents and building stock trough time. Free entry and placement is somehow limited by a public authority that keeps utility at its higher possible state at each time step. Thirdly, we abandon the assumption that neighbourhood quality is related to the density of available activities or the density of green space within a given neighbourhood, but replace this with the access to a diversity of urban and green opportunities depending on their use frequency (daily walk, playground, hiking in forest,…). This is a very important change in geocomputational terms since simple focal functions can no longer be used to represent externalities in simulation models. The gradual construction of roads and houses change gradually the nature of the landscape and the value taken out of it, typically by dividing green patches into parts, creating detours to access bigger parks, shadowing effects, etc. In addition, this requires that landscape objects are represented as vectors, not cells, which is a second important change in geocomputational terms. To some extent this brings urban simulation models closer to landscape ecology and graph-based approaches. In this paper we explore and contrast the effects of the three mechanisms mentioned above on the resulting urban morphology. [less ▲]

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See detailDielectric breakdown and urban growth: Morphological similarities or conceptual links?
Frankhauser, Pierre; Peeters, Dominique; Caruso, Geoffrey UL et al

Scientific Conference (2015, September)

Urban dynamics generate sprawl patterns that reveals in many cases fractal-like properties. This is the reason why a couple of research projects focused on how to simulate the growth of such patterns ... [more ▼]

Urban dynamics generate sprawl patterns that reveals in many cases fractal-like properties. This is the reason why a couple of research projects focused on how to simulate the growth of such patterns while respecting their fractal features. It is well-known that cellular automata can be used for generating random fractal structures. This holds e.g. for certain models developed in physics like DLA (Diffusion Limited Aggregation) or DBM (Dielectric Breakdown Models) and thus such models inspired urban growth simulation models. However in physics these models are based on a transcription of the underlying physical laws, combining electrodynamics and thermodynamics. Hence DLA and DBM are not just morpho-descriptive, but refer to explanatory approaches. However it seems difficult to establish a direct causal link between these approaches and urban growth. The goal of several recent models was to introduce a more explanatory approach for simulating the emergence of urban patterns by means of cellular automata. Following this objective, micro-economic reasoning has been used for describing households’ residential choice behaviour and constituting the driving force of cellular automata. These models assume that households settle down subsequently in the vicinity of a preexisting CBD where jobs are localized. Households have preferences for social and green amenities in their neighbourhood. Even if these approaches can explain some properties of urban growth processes, like leapfrogging, the patterns generated do not really show fractal properties, even if some morphological analogies with DBM have been identified. Moreover in the enunciated models, the dynamics is driven only by the evaluation of households who to want to settle down in the already existing city region. The City Administration is supposed to construct new road segments without consequences for the budget of the households. This is questionable. Here we introduce a model that starts from a pre-existing cross-like street network with a CBD at the crossing point where all kinds of services, shopping amenities and jobs are concentrated. However we introduce a series of new mechanisms. First, new arriving households use the utility of already located households as a reference. Second a tax per household is introduced for maintaining the existing street network and the infrastructures of the pre-existing centre. New households can improve the utility of urban population by contributing to these fixed costs. However if a well evaluated site needs to be connected by a new road segment to the existing street network, this will increase the costs for total maintenance of the street network and thus the tax. Third, each household wants to benefit from green amenities for different use (daily walks, playground, hiking…) but the construction of side branches of the road network can impede direct accesses to open landscapes and can generate supplementary travel costs thus impacting the budget of households. This “shadowing effect” reminds some mechanisms of the DBM-models. The model thus combines different aspects acting positively or negatively on the households’ utility and budget. According to the expected changes to their indirect utility function, the households who have settled down earlier in the city will not be in favour of accepting new households. This paper focuses on the conceptualization of the model and on the morphological properties of the emerging patterns. It is illustrated by several simulation results. [less ▲]

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See detailLand Use and Transport Interaction Models - Where is the limit?
Caruso, Geoffrey UL; Jones, Jonathan; Thomas, Isabelle et al

Scientific Conference (2015, July 08)

Land Use and Transport Interaction (LUTI) models are precious tools to integrating the many impacts and feedbacks of the location of activities on transport infrastructures and vice versa. In that sense ... [more ▼]

Land Use and Transport Interaction (LUTI) models are precious tools to integrating the many impacts and feedbacks of the location of activities on transport infrastructures and vice versa. In that sense, applying LUTI models is key to delivering regulation and planning options for urban and transport sustainability. For they have been used in practice to guide urban planners and help transport policy since the 1960’s and the pioneering work of Lowry (1964). The effectiveness of LUTI models as decision support tools is generally well accepted by transport and planning researchers and by practitioners, despite sailing through troubled waters between consultancy secrets, politically led options, data problems, rule of thumb calibration, and model openness and transparency. At the turn of the millennium, LUTI models have developed from aggregate zone-based models to micro representation of space and disaggregated representation of agents, following increased computing capacity and availability of better GIS and individual data. As demonstrated by Wegener (2011) this modeling shift however goes with costs that impede empirical validation and further adoption in planning. LUTI modelers have long recognized that the different processes within LUTI models act and interface at different speeds (Wegener, 1986). The further granularity accompanying disaggregation then leads to dynamics that are trickier to handle. As argued by Anas (2013), LUTI models need clearer definitions and a stricter use of urban economics concepts. Likewise, we argue in this paper that LUTI models also need to take better care of geographical knowledge and spatial biases. They require the analysis of the robustness of model outcomes to the choice of spatial units and MAUP, which is analyzed by Jones et al. (2013) but also the effect of changing urban system boundaries, which is under focus here. Defining the limits of a coherent study area for modeling is actually questioning the delimitation of a city or urban region. This is obviously not a new question to geographers and economists but it impacts deeply on how inner stocks (population, firms, …) and external flows (traffic, labor,…) are modeled in LUTI models and therefore on their outcome. From intuition and practice, we hypothesize that there is strong inertia in LUTI models outcomes because the many parameters and variables that are present in these models are eventually strongly constrained by the geographical structure considered (monocentric, polycentric, including exurbs or not, etc.). Where the outer limit of a model is traced not only impacts the internal components of the city but also questions the problem of the limits between two cities, which is not trivial. First, we perform a meta-analysis of recent LUTI applications in European contexts based on 19 peer-reviewed articles. The lack of definition of the study area is striking. Interestingly in the first LUTI implementation, Lowry (1964) explicitly mentioned the use of an estimate of the commutershed of Pittsburgh for the next 20 years. The lack of explicit choice in later literature with models of increased complexity, stresses the need for guidelines that could improve practice in order to improve the comparability of applications and the generalization of results where possible. Second, we perform simulations on a synthetic city system using UrbanSim (Waddell et al., 2003). We gradually vary the spatial limits of the system from an inner center monocentric system to a polycentric city region. We also vary population and employment endowments, hence commuting patterns. Our simulations show that LUTI results are highly impacted by the change of limits and therefore suggest a reason why LUTI models are sensitive to large parametric shocks only. Our paper confirms that the absence of a strict theoretical rationale for city delineation weakens the effectiveness of LUTI models. References Anas, A. 2013. A response to the guest editorial: economics as the science for urban modeling. Environment and Planning B, 40 (6), 955 – 958 Jones, J., Peeters, D and Thomas, I. 2013. On the Influence of Scale on Urban Planning Evaluations by LUTI models. ASRDLF Congress 2013. Lowry, I.S. 1964. A model of metropolis. Memorandum RM 4035 Rand Corporation, Santa-Monica. 136p Waddell, P., Borning, A., Noth, M., Freier, N., Becke, M. and Ulfarsson, G. 2003. Microsimulation of Urban Development and Location Choices: Design and Implementation of UrbanSim. Networks and Spatial Economics, 3 (1), 43-67 Wegener, M., Gnad, F., Vannahme, M. 1986. The time scale of urban change. In Hutchinson, B and Batty, M. (Eds), Advances in Urban Systems Modelling. North-Holland, Amsterdam, 145–197. Wegener, M. 2011. From macro to micro - how much micro is too much? Transport Reviews, 31, 161–177 [less ▲]

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See detailOn the delineation of cities in applied LUTI models in Europe: bibliography and simulations
Thomas, Isabelle; Caruso, Geoffrey UL; Gerber, Philippe et al

Scientific Conference (2015, July)

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See detailEmergence of leapfrogging from residential choice with endogenous green space: analytical results
Peeters, Dominique; Caruso, Geoffrey UL; Cavailhès, Jean et al

in Journal of Regional Science (2015), 55(3), 491-512

Leapfrog development is a typical form of sprawl. This paper aims at analyzing the existence, size, and persistence of leapfrogging in a dynamic urban economic model with endogenous green amenities. We ... [more ▼]

Leapfrog development is a typical form of sprawl. This paper aims at analyzing the existence, size, and persistence of leapfrogging in a dynamic urban economic model with endogenous green amenities. We analyze whether incoming households choose to settle at the fringe of the city or to jump further away depending on their preferences and the structure of the city. We first provide an analytical treatment of the conditions and characteristics under which a first leapfrog occurs and show how the optimal choice is affected by the size of the city, income, commuting costs, as well as the size of the area where green amenities are considered. We then study how further leapfrogging and multiple urban rings may appear and be maintained in the long-run equilibrium, and how infill processes take place through time. [less ▲]

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See detailHousing land transaction data and structural econometric estimation of preference parameters for urban economic simulation models
Caruso, Geoffrey UL; Cavailhès, Jean; Peeters, Dominique et al

in Data in Brief (2015), 5

This paper describes a dataset of 6284 land transactions prices and plot surfaces in 3 medium-sized cities in France (Besançon, Dijon and Brest). The dataset includes road accessibility as obtained from a ... [more ▼]

This paper describes a dataset of 6284 land transactions prices and plot surfaces in 3 medium-sized cities in France (Besançon, Dijon and Brest). The dataset includes road accessibility as obtained from a minimization algorithm, and the amount of green space available to households in the neighborhood of the transactions, as evaluated from a land cover dataset. Further to the data presentation, the paper describes how these variables can be used to estimate the non-observable parameters of a residential choice function explicitly derived from a microeconomic model. The estimates are used by Caruso et al. (2015) to run a calibrated microeconomic urban growth simulation model where households are assumed to trade-off accessibility and local green space amenities. [less ▲]

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See detailGreener and larger neighbourhoods make cities more sustainable! A 2D urban economics perspective
Caruso, Geoffrey UL; Cavailhès, Jean; Peeters, Dominique et al

in Computers, Environment & Urban Systems (2015)

We analyse urban growth forms by means of a 2D microeconomic model where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow more densely when households ... [more ▼]

We analyse urban growth forms by means of a 2D microeconomic model where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow more densely when households have the possibility to enlarge the neighbourhood in which they value green space, thus emphasising the importance of neighbourhood planning in particular for facilitating short trips and views of green amenities. We also show by simulation that the size and form of the city, relative to the size and form of neighbourhoods, impact on the decision of households to leapfrog land or not, thus impacting on the emergence of scattered urbanisation patterns. We conclude that carefully addressing the spatial arrangement of green space and buildings and facilitating trips within neighbourhood units constitute an effective policy lever and an attractive way to deliver more sustainable cities. We further argue that our theoretical experiment with complementary analytical and computer-based simulation provides micro-economic reasoning to the main elements of the Garden City and neighbourhood unit planning concepts. [less ▲]

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See detailHow green neighbourhoods make cities more compact? A 2D microeconomic perspective
Caruso, Geoffrey UL; Cavailhes, Jean; Peeters, Dominique et al

Scientific Conference (2014)

We analyse urban growth forms by means of a 2D microeconomic model with no symmetry assumption where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow ... [more ▼]

We analyse urban growth forms by means of a 2D microeconomic model with no symmetry assumption where households value green space at neighbourhood scale. We analytically demonstrate that cities can grow more densely when households have the possibility to enlarge the neighbourhood in which they value green space, thus emphasizing the importance of neighbourhood planning in particular for facilitating short trips and view to amenities. We also show by simulation that the size and form of the city, relative to the size and form of neighbourhoods, impact on the decision of households to leapfrog agricultural land or not, hence impact on the emergence of sprawl patterns. We conclude that carefully addressing the spatial arrangement of green space and activities within neighbourhoods may constitute an effective policy lever in some urban contexts and a positive incentive to a more compact development. [less ▲]

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See detailEmergence of scattered and leapfrog urban development from analytical results to complex simulation outputs with realistic calibration
Caruso, Geoffrey UL; Cavailhès, Jean; Frankhauser, Pierre et al

Scientific Conference (2013)

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See detailEmergence of scattered and leapfrog urban development from analytical results to complex simulation outputs with realistic calibration
Caruso, Geoffrey UL; Cavailhès, Jean; Frankhauser, Pierre et al

Scientific Conference (2013)

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See detailHow neighbourhood interactions influence urban sprawl
Frankhauser, Pierre; Caruso, Geoffrey UL; Peeters, Dominique et al

Scientific Conference (2011)

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See detailMorphological similarities between DBM and a microeconomic model of sprawl
Caruso, Geoffrey UL; Vuidel, Gilles; Cavailhès, Jean et al

in Journal of Geographical Systems (2011), 13(1), 31-48

We present a model that simulates the growth of a metropolitan area on a 2D lattice. The model is dynamic and based on microeconomics. Households show preferences for nearby open-spaces and neighbourhood ... [more ▼]

We present a model that simulates the growth of a metropolitan area on a 2D lattice. The model is dynamic and based on microeconomics. Households show preferences for nearby open-spaces and neighbourhood density. They compete on the land market. They travel along a road network to access the CBD. A planner ensures the connectedness and maintenance of the road network. The spatial pattern of houses, green-spaces and road network self-organises, emerging from agents individualistic decisions. We perform several simulations and vary residential preferences. Our results show morphologies and transition phases that are similar to Dieletric Breakdown Models (DBM). Such similarities were observed earlier by other authors, but we show here that it can be deducted from the functionning of the land market and thus explicitly connected to urban economic theory. [less ▲]

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See detailS-GHOST: Un modèle d'auto-organisation de l'étalement urbain et du réseau de transport
Caruso, Geoffrey UL; Cavailhès, Jean; Frankhauser, Pierre et al

in Antoni, Jean-Philippe (Ed.) Modéliser la ville: formes urbaines et politiques de transport (2011)

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See detailMorphological similarities between DBM and an economic geography model of city growth
Cavailhès, Jean; Frankhauser, Pierre; Caruso, Geoffrey UL et al

in Zhou, Jie (Ed.) Complex Sciences (2009)

An urban microeconomic model of households evolving in a 2D cellular automata allows to simulate the growth of a metropolitan area where land is devoted to housing, road network and agricultural/green ... [more ▼]

An urban microeconomic model of households evolving in a 2D cellular automata allows to simulate the growth of a metropolitan area where land is devoted to housing, road network and agricultural/green areas. This system is self-organised: based on individualistic decisions of economic agents who compete on the land market, the model generates a metropolitan area with houses, roads, and agriculture. Several simulation are performed. The results show strong similarities with physical Dieletric breakdown models (DBM). In particular, phase transitions in the urban morphology occur when a control parameter reaches critical values. Population density in our model and the electric potential in DBM play similar roles, which can explain these resemblances. [less ▲]

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See detailThe emergence of leapfrogging in an urban growth model combining an economic approach and cellular automata
Frankhauser, Pierre; Caruso, Geoffrey UL; Peeters, Dominique et al

Scientific Conference (2009)

Detailed reference viewed: 27 (1 UL)