240 research outputs found
¿Patrimonio o ciudad?: limitaciones de los instrumentos de intervención urbanística en los Conjuntos Históricos
La conservación de los conjuntos históricos se encomienda en las últimas décadas a los instrumentos de intervención urbanística. Una vez transcurrido el tiempo de la primera generación de planes y programas destinados a la protección y a la recuperación de estos ámbitos, es tiempo de evaluar los resultados obtenidos. La investigación que desarrollo pretende analizar no solo el estado de los valores arquitectónicos, sino también las características sociales y funcionales tradicionales que son parte del patrimonio que se quiere conservar. Una representación de los 140 conjuntos Históricos de la comunidad de Castilla y León están siendo analizados: la aplicación de Planes Generales, Planes Especiales y Áreas de Rehabilitación Integral serán confrontados con sus resultados en un trabajo que pretende sentar las bases para mejorar los efectos obtenidos por las siguientes generaciones de instrumentos.In the last years the conservation of historic areas has been mainly entrusted to planning instruments. We have a first generation of Special Plans and Urban Programs intended for protecting and recovering these areas, so it is time to evaluate the results. The research aims to analyse not only the state of art regarding the conservation of architectural values, but also the traditional social and functional characteristics that are part of the heritage that is supposed to be preserved. A representative part of the 140 historic areas of the community of Castilla y León will be analysed: Town Planning and Special Planning application, even Rehabilitation Areas will be confronted with their results. The work aims to serve and improve the basis for the next generation of urban intervention instruments.Peer Reviewe
El papel del urbanismo y del proyecto de ciudad en la conservación del patrimonio: una mirada al contexto francés
Respecto a la conservación del patrimonio urbano, se viene insistiendo en la importancia de su
planteamiento dentro del proyecto de ciudad, desde las cartas y documentos internacionales o incluso
desde ciertos planes de la década de 1970. La legislación y la aplicación práctica generalizada en Europa, a
pesar de algunas reconocidas intenciones, no terminan por acometerlo de esta manera y a veces se pierde
en la maraña de planes sectoriales y en la subdivisión administrativa del territorio. Una mirada al panorama
francés nos permite comprender esta situación y algunos apuntes de su evolución reciente. En particular se
abordaran las políticas francesas de Sectores a Salvaguardar, y las Zonas de Protección del Patrimonio y su
relación con otros instrumentos de planeamiento.Regarding the conservation of urban heritage, many international charts or even some examples of town
planning since the 1970s has been insisting on the importance of its approach within the proposed whole
city. Despite some recognized intentions, legislation and specially practise in Europe eventually don’t tackle it
in this way and sometimes gets lost in between sectorial plans and the administrative subdivision of territory.
A quick look at French panorama serves us to understand this situation and the present evolution. In
particular, we will address French policies as Secteurs Sauvegardés or Zones de Protection du Patrimoine
and its relationship to other planning instruments.Peer Reviewe
Temporal networks: slowing down diffusion by long lasting interactions
Interactions among units in complex systems occur in a specific sequential
order thus affecting the flow of information, the propagation of diseases, and
general dynamical processes. We investigate the Laplacian spectrum of temporal
networks and compare it with that of the corresponding aggregate network.
First, we show that the spectrum of the ensemble average of a temporal network
has identical eigenmodes but smaller eigenvalues than the aggregate networks.
In large networks without edge condensation, the expected temporal dynamics is
a time-rescaled version of the aggregate dynamics. Even for single sequential
realizations, diffusive dynamics is slower in temporal networks. These
discrepancies are due to the noncommutability of interactions. We illustrate
our analytical findings using a simple temporal motif, larger network models
and real temporal networks.Comment: 5 pages, 2 figures, v2: minor revision + supplemental materia
Dynamic Modeling of the Electric Transportation Network
We introduce a model for the dynamic self-organization of the electric grid.
The model is characterized by a conserved magnitude, energy, that can travel
following the links of the network to satisfy nodes' load. The load fluctuates
in time causing local overloads that drive the dynamic evolution of the network
topology. Our model displays a transition from a fully connected network to a
configuration with a non-trivial topology and where global failures are
suppressed. The most efficient topology is characterized by an exponential
degree distribution, in agreement with the topology of the real electric grid.
The model intrinsically presents self-induced break-down events, which can be
thought as representative of real black-outs.Comment: (e.g. 7 pages, 5 figures
Collective intelligence: aggregation of information from neighbors in a guessing game
Complex systems show the capacity to aggregate information and to display
coordinated activity. In the case of social systems the interaction of
different individuals leads to the emergence of norms, trends in political
positions, opinions, cultural traits, and even scientific progress. Examples of
collective behavior can be observed in activities like the Wikipedia and Linux,
where individuals aggregate their knowledge for the benefit of the community,
and citizen science, where the potential of collectives to solve complex
problems is exploited. Here, we conducted an online experiment to investigate
the performance of a collective when solving a guessing problem in which each
actor is endowed with partial information and placed as the nodes of an
interaction network. We measure the performance of the collective in terms of
the temporal evolution of the accuracy, finding no statistical difference in
the performance for two classes of networks, regular lattices and random
networks. We also determine that a Bayesian description captures the behavior
pattern the individuals follow in aggregating information from neighbors to
make decisions. In comparison with other simple decision models, the strategy
followed by the players reveals a suboptimal performance of the collective. Our
contribution provides the basis for the micro-macro connection between
individual based descriptions and collective phenomena.Comment: 9 pages, 9 figure
Competition in the presence of aging: order, disorder, and synchronized collective behavior
We study the stochastic dynamics of coupled states with transition
probabilities depending on local persistence, this is, the time since a state
has changed. When the population has a preference to adopt older states the
system orders quickly due to the dominance of the old state. When preference
for new states prevails, the system can show coexistence of states or
synchronized collective behavior resulting in long ordering times. In this
case, the magnetization of the system oscillates around .
Implications for social systems are discussed.Comment: 5 pages, 5 figures, lette
From continuous to discontinuous transitions in social diffusion
Models of social diffusion reflect processes of how new products, ideas or
behaviors are adopted in a population. These models typically lead to a
continuous or a discontinuous phase transition of the number of adopters as a
function of a control parameter. We explore a simple model of social adoption
where the agents can be in two states, either adopters or non-adopters, and can
switch between these two states interacting with other agents through a
network. The probability of an agent to switch from non-adopter to adopter
depends on the number of adopters in her network neighborhood, the adoption
threshold and the adoption coefficient , two parameters defining a Hill
function. In contrast, the transition from adopter to non-adopter is
spontaneous at a certain rate . In a mean-field approach, we derive the
governing ordinary differential equations and show that the nature of the
transition between the global non-adoption and global adoption regimes depends
mostly on the balance between the probability to adopt with one and two
adopters. The transition changes from continuous, via a transcritical
bifurcation, to discontinuous, via a combination of a saddle-node and a
transcritical bifurcation, through a supercritical pitchfork bifurcation. We
characterize the full parameter space. Finally, we compare our analytical
results with Montecarlo simulations on annealed and quenched degree regular
networks, showing a better agreement for the annealed case. Our results show
how a simple model is able to capture two seemingly very different types of
transitions, i.e., continuous and discontinuous and thus unifies underlying
dynamics for different systems. Furthermore the form of the adoption
probability used here is based on empirical measurements.Comment: 7 pages, 3 figure
Voter model dynamics in complex networks: Role of dimensionality, disorder and degree distribution
We analyze the ordering dynamics of the voter model in different classes of
complex networks. We observe that whether the voter dynamics orders the system
depends on the effective dimensionality of the interaction networks. We also
find that when there is no ordering in the system, the average survival time of
metastable states in finite networks decreases with network disorder and degree
heterogeneity. The existence of hubs in the network modifies the linear system
size scaling law of the survival time. The size of an ordered domain is
sensitive to the network disorder and the average connectivity, decreasing with
both; however it seems not to depend on network size and degree heterogeneity.Comment: (8 pages, 12 figures, for simililar work visit
http://www.imedea.uib.es/physdept/
Particle velocity controls phase transitions in contagion dynamics
Interactions often require the proximity between particles. The movement of
particles, thus, drives the change of the neighbors which are located in their
proximity, leading to a sequence of interactions. In pathogenic contagion,
infections occur through proximal interactions, but at the same time the
movement facilitates the co-location of different strains. We analyze how the
particle velocity impacts on the phase transitions on the contagion process of
both a single infection and two cooperative infections. First, we identify an
optimal velocity (close to half of the interaction range normalized by the
recovery time) associated with the largest epidemic threshold, such that
decreasing the velocity below the optimal value leads to larger outbreaks.
Second, in the cooperative case, the system displays a continuous transition
for low velocities, which becomes discontinuous for velocities of the order of
three times the optimal velocity. Finally, we describe these characteristic
regimes and explain the mechanisms driving the dynamics.Comment: 9 pages, 5 figures, 12 supplementary figure
Bayesian decision making in human collectives with binary choices
Here we focus on the description of the mechanisms behind the process of
information aggregation and decision making, a basic step to understand
emergent phenomena in society, such as trends, information spreading or the
wisdom of crowds. In many situations, agents choose between discrete options.
We analyze experimental data on binary opinion choices in humans. The data
consists of two separate experiments in which humans answer questions with a
binary response, where one is correct and the other is incorrect. The questions
are answered without and with information on the answers of some previous
participants. We find that a Bayesian approach captures the probability of
choosing one of the answers. The influence of peers is uncorrelated with the
difficulty of the question. The data is inconsistent with Weber's law, which
states that the probability of choosing an option depends on the proportion of
previous answers choosing that option and not on the total number of those
answers. Last, the present Bayesian model fits reasonably well to the data as
compared to some other previously proposed functions although the latter
sometime perform slightly better than the Bayesian model. The asset of the
present model is the simplicity and mechanistic explanation of the behavior.Comment: 8 pages, 6 figures, 1 tabl
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