54,943 research outputs found
Spatial Measures of Urban Systems: from Entropy to Fractal Dimension
A type of fractal dimension definition is based on the generalized entropy
function. Both entropy and fractal dimension can be employed to characterize
complex spatial systems such as cities and regions. Despite the inherent
connect between entropy and fractal dimension, they have different application
scopes and directions in urban studies. This paper focuses on exploring how to
convert entropy measurement into fractal dimension for the spatial analysis of
scale-free urban phenomena using ideas from scaling. Urban systems proved to be
random prefractal and multifractals systems. The entropy of fractal cities
bears two typical properties. One is the scale dependence. Entropy values of
urban systems always depend on the scales of spatial measurement. The other is
entropy conservation. Different fractal parts bear the same entropy value. Thus
entropy cannot reflect the spatial heterogeneity of fractal cities in theory.
If we convert the generalized entropy into multifractal spectrums, the problems
of scale dependence and entropy homogeneity can be solved to a degree for urban
spatial analysis. The essence of scale dependence is the scaling in cities, and
the spatial heterogeneity of cities can be characterized by multifractal
scaling. This study may be helpful for the students to describe and understand
spatial complexity of cities.Comment: 27 page, 9 figure, 5 table
On the Perturbation of Self-Organized Urban Street Networks
We investigate urban street networks as a whole within the frameworks of
information physics and statistical physics. Urban street networks are
envisaged as evolving social systems subject to a Boltzmann-mesoscopic entropy
conservation. For self-organized urban street networks, our paradigm has
already allowed us to recover the effectively observed scale-free distribution
of roads and to foresee the distribution of junctions. The entropy conservation
is interpreted as the conservation of the surprisal of the city-dwellers for
their urban street network. In view to extend our investigations to other urban
street networks, we consider to perturb our model for self-organized urban
street networks by adding an external surprisal drift. We obtain the statistics
for slightly drifted self-organized urban street networks. Besides being
practical and manageable, this statistics separates the macroscopic evolution
scale parameter from the mesoscopic social parameters. This opens the door to
observational investigations on the universality of the evolution scale
parameter. Ultimately, we argue that the strength of the external surprisal
drift might be an indicator for the disengagement of the city-dwellers for
their city.Comment: 22 pages, 4 figures + 1 table, LaTeX2e+BMCArt+AmSLaTeX+enote
Thermodynamic entropy as an indicator for urban sustainability?
As foci of economic activity, resource consumption, and the production of material waste and pollution, cities represent both a major hurdle and yet also a source of great potential for achieving the goal of sustainability. Motivated by the desire to better understand and measure sustainability in quantitative terms we explore the applicability of thermodynamic entropy to urban systems as a tool for evaluating sustainability. Having comprehensively reviewed the application of thermodynamic entropy to urban systems we argue that the role it can hope to play in characterising sustainability is limited. We show that thermodynamic entropy may be considered as a measure of energy efficiency, but must be complimented by other indices to form part of a broader measure of urban sustainability
Thermodynamic entropy as an indicator for urban sustainability?
As foci of economic activity, resource consumption, and the production of material waste and pollution, cities represent both a major hurdle and yet also a source of great potential for achieving the goal of sustainability. Motivated by the desire to better understand and measure sustainability in quantitative terms we explore the applicability of thermodynamic entropy to urban systems as a tool for evaluating sustainability. Having comprehensively reviewed the application of thermodynamic entropy to urban systems we argue that the role it can hope to play in characterising sustainability is limited. We show that thermodynamic entropy may be considered as a measure of energy efficiency, but must be complimented by other indices to form part of a broader measure of urban sustainability
Between order and disorder: a 'weak law' on recent electoral behavior among urban voters?
A new viewpoint on electoral involvement is proposed from the study of the
statistics of the proportions of abstentionists, blank and null, and votes
according to list of choices, in a large number of national elections in
different countries. Considering 11 countries without compulsory voting
(Austria, Canada, Czech Republic, France, Germany, Italy, Mexico, Poland,
Romania, Spain and Switzerland), a stylized fact emerges for the most populated
cities when one computes the entropy associated to the three ratios, which we
call the entropy of civic involvement of the electorate. The distribution of
this entropy (over all elections and countries) appears to be sharply peaked
near a common value. This almost common value is typically shared since the
1970's by electorates of the most populated municipalities, and this despite
the wide disparities between voting systems and types of elections. Performing
different statistical analyses, we notably show that this stylized fact reveals
particular correlations between the blank/null votes and abstentionists ratios.
We suggest that the existence of this hidden regularity, which we propose to
coin as a `weak law on recent electoral behavior among urban voters', reveals
an emerging collective behavioral norm characteristic of urban citizen voting
behavior in modern democracies. Analyzing exceptions to the rule provide
insights into the conditions under which this normative behavior can be
expected to occur.Comment: Version 1: main text 19 pages, 13 figures, 2 tables; Supporting
Information: 19 pages. Version 2: minor correction
Spatial entropy: a small town perspective - case study: the town of Marghita
The concept of "spatial entropy" developed by Michael Batty (1974) was
primarily used to test different hypotheses concerning the distribution and density of
population in great cities like New York, London, Los Angeles. Subsequently spatial
entropy was adapted in urban and regional studies, where two types of research have
been outlined: - "descriptive statistics" and "MaxEnt" method (Esmer 2005). Three
characteristic elements related to the three components of sustainable development
(society, economy and environment) have been considered to shape the degree of entropy
for the urban system Marghita, namely: population, turnover and green spaces. The
determination of the entropy degree for the Marghita urban system was achieved by
applying statistical physics functions on open systems, related to the three pillars of
sustainable development. The three domains are represented by a series of dynamic and
complex elements characterized by input and output streams, influenced by endogenous
factors character
Structure Entropy, Self-Organization, and Power Laws in Urban Street Networks: Evidence for Alexander's Ideas
Easy and intuitive navigability is of central importance in cities. The actual scale-free networking of urban street networks in their topological space, where navigation information is encoded by mapping roads to nodes and junctions to links between nodes, has still no simple explanation. Emphasizing the road-junction hierarchy in a holistic and systematic way leads us to envisage urban street networks as evolving social systems subject to a Boltzmann-mesoscopic entropy conservation. This conservation, which we may interpret in terms of surprisal, ensures the passage from the road-junction hierarchy to a scale-free coherence. To wit, we recover the actual scale-free probability distribution for natural roads in self-organized cities. We obtain this passage by invoking Jaynes's Maximum Entropy principle (statistical physics), while we capitalize on modern ideas of quantification (information physics) and well known results on structuration (lattice theory) to measure the information network entropy. The emerging paradigm, which applies to systems with more intricate hierarchies as actual cities, appears to reflect well the influential ideas on cities of the urbanist Christopher Alexander
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