Catálogo de publicaciones - libros

Patients with hemorrhagic stroke are usually admitted for observation to an intensive care unit (ICU). A smaller percentage of patients with ischemic stroke are also admitted, as well as patients with cerebral venous thrombosis or those who have undergone carotid endarterectomy. All these patients are at risk for seizures. Those with hemorrhagic stroke are usually at two to three times higher risk than those with ischemic stroke, but several characteristics of the stroke modify the risk for having a seizure. In most cases an early seizure (within the first few days after the ictus) has a different significance from a late seizure (after the patient has been discharged from the ICU or the hospital). In addition, a significant role is played by the treatment offered to these patients, either medical, surgical, or endovascular. Despite an abundance of studies examining the incidence and characteristics of poststroke seizures, there are several questions still to be answered regarding the institution and duration of the appropriate treatment.

This paper discusses the social significance, theoretical rationale and methodological and technological characteristics of complex artificial environments of the 21 century. It starts by identifying a social change, the essence of which is that cities and urbanism are growing in significance, to the extent that one can speak of a . The paper goes on to explore urban theory and the view that cities are complex, self-organizing, artificial environments, and that the theorization of their dynamics should start from the first principles of humans’ cognitive capabilities. Finally, the paper considers the methodologies of agent base, cellular automata and advanced virtual reality simulators as tools for studying cities as self-organizing complex environments.

In this paper I point at specific differences between natural and artificial environments with respect to recognition procedures by computers. In general the artificial environment appears far more regular than the natural environment. Basic computer procedures for pattern recognition are outlined. Special emphasis is laid on the semantics of a city where the study of languages as semantic networks is invoked as a paradigm where basic concepts of synergetics such as order parameters and the slaving principle are used.

This chapter deals with issues arising from a central theme in contemporary computer modeling — visualization. We first tie visualization to varieties of modeling along the continuum from iconic to symbolic and then focus on the notion that our models are so intrinsically complex that there are many different types of visualization that might be developed in their understanding and implementation. This focuses the debate on the very way of ‘doing science’ in that patterns and processes of any complexity can be better understood through visualizing the data, the simulations, and the outcomes that such models generate. As we have grown more sensitive to the problem of complexity in all systems, we are more aware that the twin goals of parsimony and verifiability which have dominated scientific theory since the ‘Enlightenment’ are up for grabs: good theories and models must ‘look right’ despite what our statistics and causal logics tell us. Visualization is the cutting edge of this new way of thinking about science but its styles vary enormously with context. Here we define three varieties: visualization of complicated systems to make things simple or at least explicable, which is the role of pedagogy; visualization to explore unanticipated outcomes and to refine processes that interact in unanticipated ways; and visualization to enable end users with no prior understanding of the science but a deep understanding of the problem to engage in using models for prediction, prescription, and control. We illustrate these themes with a model of an agricultural market which is the basis of modern urban economics — the von Thünen model of land rent and density; a model of urban development based on interacting spatial and temporal processes of land development — the model; and a pedestrian model of human movement at the fine scale where control of such movements to meet standards of public safety is intrinsically part of the model about which the controllers know intimately.

The development of a theory of complex systems that establish bridges between disciplines of the natural and social sciences appears together as an opportunity and as a challenge for urban modeling. Borrowing concepts and tools from formalised disciplines may help to more satisfying expressions of urban theories and to a better understanding of abstract processes that are behind urban dynamics. However, the specific features of social systems should not be neglected or underestimated while operating these transfers. Proper adapted ontologies have to be preserved for urban entities and the new experiments should be able to become part of the previously existing urban knowledge, helping to revise it, not replacing it.

The Center for 3D GeoInformation at Aalborg University (DK) became a reality in 2001. Among the many activities in the center, there is one that goes through all the others as an important red line. That is the development of a general object-oriented system for real-time 3D visualization of geographically based Virtual Environments, called GRIFINOR. This paper will reveal some of the considerations and aspects that have been discussed in the preliminary design of GRIFINOR. The system involves use of several different methods for semi-automatic generation of 3D objects from LIDAR data, Orthophotos, building footprints and data from various public registers. At the moment the system is only prepared for generation of static physical elements such as buildings, but later the system will be able to visualize traditional geoinformation such as socio-economic attribute values on “top” of the Virtual Environment. The buildings are generated as objects based on representation in the 2D technical/topographical map, the LIDAR data and information about each building from the national building and dwelling registry (BBR). After each entity is generated as an object it is saved in a custom built object database. This database is the heart of the system and several specific issues regarding the development of it will be discussed. At the front end, a 3D viewer based on a Java-driven scene graph is the core of the graphical user interface. The considerations behind a representational model for the objects will also be presented and finally some discussions about potential viewing platforms.

The Environmental Simulation Laboratory (ESLab) is one of several laboratories, research centers and planning and design organizations that have emerged in the last two decades with a configuration that focuses on complex artificial environments in general, and on cities and their dynamics, in particular. The specific experience gained at ESLab is employed in this paper to discuss the various theoretical, methodological, social and ethical issues associated with the above emerging bodies.

Automata-based models have enjoyed widespread application to urban simulation in recent years. Cellular automata (CA) and multi-agent systems (MAS) have been particularly popular. However, CA and MAS are often confused. In many instances, CA are paraphrased as agent-based models and simply re-interpreted as MAS. This is interesting from a geographical standpoint, because the two may be distinguished by their spatial attributes. First, they differ in terms of their mobility: CA cannot “move”, but MAS are mobile entities. Second, in terms of interaction, CA transmit information by diffusion over neighborhoods; MAS transmit information by themselves, moving between locations that can be at any distance from an agent’s current position. These different views on the basic geography of the system can have important implications for urban simulations developed using the tools. It may result in different space-time dynamics between model runs and may have important consequences for the use of the models as applied tools. In this chapter, a patently spatial framework for urban simulation with automata Tools is described: Geographic Automata Systems (GAS). The applicability of the GAS approach will be demonstrated with reference to practical implementations, showing how the framework can be used to develop intuitive models of urban dynamics.

The concept of Geographic Automata System (GAS) formalizes an object-based view of city structure and functioning; OBEUS software implements this view on the operational level. The paper presents the GAS paradigm and latest user-friendly version of OBEUS, the latter based on .NET technology and developed according to OODBMS logic. OBEUS boosts further development of GAS theory, especially regarding the treatment of time in models describing collectives of multiple interacting autonomous urban objects. We claim that all high-resolution urban Cellular Automata and Multi-Agent models of which we are aware can be described in GAS terms and represented as OBEUS applications. GAS and OBEUS can thus serve as a universal, transferable framework for object-based urban simulation.

In this paper I present a multi-agent simulation model of the development of a city. The model, CityDev, is based on agents, goods and markets. Each agent (family, industrial firm, developer, etc.) produces goods by using other goods, and trades the goods in the markets. Each good has a price, and the monetary aspects are included in the simulation. When agents produce goods and interact in the markets, the urban fabric is built and transformed. The computer model (simulator) runs on a 3-D spatial pattern organized in cubic cells. In the present paper the model is described and results are shown.