Artículos con la etiqueta ‘computación’

City versus wetland: Predicting urban growth in the Vecht area with a cellular automaton model

Por • 14 abr, 2013 • Category: sociologia

There are many studies dealing with the protection or restoration of wetlands and the sustainable economic growth of cities as separate subjects. This study investigates the conflict between the two in an area where city growth is threatening a protected wetland area. We develop a stochastic cellular automaton model for urban growth and apply it to the Vecht area surrounding the city of Hilversum in the Netherlands, using topographic maps covering the past 150 years. We investigate the dependence of the urban growth pattern on the values associated with the protected wetland and other types of landscape surrounding the city. The conflict between city growth and wetland protection is projected to occur before 2035, assuming full protection of the wetland. Our results also show that a milder protection policy, allowing some of the wetland to be sacrificed, could be beneficial for maintaining other valuable landscapes.



The Third Life of Quantum Logic: Quantum Logic Inspired by Quantum Computing

Por • 16 feb, 2013 • Category: Leyes

We begin by discussing the history of quantum logic, dividing it into three eras or lives. The first life has to do with Birkhoff and von Neumann’s algebraic approach in the 1930’s. The second life has to do with attempt to understand quantum logic as logic that began in the late 1950’s and blossomed in the 1970’s. And the third life has to do with recent developments in quantum logic coming from its connections to quantum computation. We discuss our own work connecting quantum logic to quantum computation (viewing quantum logic as the logic of quantum registers storing qubits), and make some speculations about mathematics based on quantum principles.



Mathematics in the Age of the Turing Machine

Por • 13 feb, 2013 • Category: Opinion

The article gives a survey of mathematical proofs that rely on computer calculations and formal proofs. Computers have rapidly become so pervasive in mathematics that future generations may look back to this day as a golden dawn. A comprehensive survey is out of the question. It would almost be like asking for a summary of applications of symmetry to mathematics. Computability – like symmetry – is a wonderful structural property that some mathematical objects possess that makes answers flow more readily wherever it isfound.



Complexity of equivalence relations and preorders from computability theory

Por • 12 feb, 2013 • Category: Crítica

We study the relative complexity of equivalence relations and preorders from computability theory and complexity theory. Given binary relations $R, S$, a componentwise reducibility is defined by $ R\le S \iff \ex f \, \forall x, y \, [xRy \lra f(x) Sf(y)]. $ Here $f$ is taken from a suitable class of effective functions. For us the relations will be on natural numbers, and $f$ must be computable. We show that there is a $\Pi_1$-complete equivalence relation, but no $\Pi k$-complete for $k \ge 2$. We show that $\Sigma k$ preorders arising naturally in the above-mentioned areas are $\Sigma k$-complete. This includes polynomial time $m$-reducibility on exponential time sets, which is $\Sigma 2$, almost inclusion on r.e.\ sets, which is $\Sigma 3$, and Turing reducibility on r.e.\ sets, which is $\Sigma 4$.



Towards common-sense reasoning via conditional simulation: legacies of Turing in Artificial Intelligence

Por • 25 dic, 2012 • Category: Crítica

The problem of replicating the flexibility of human common-sense reasoning has captured the imagination of computer scientists since the early days of Alan Turing’s foundational work on computation and the philosophy of artificial intelligence. In the intervening years, the idea of cognition as computation has emerged as a fundamental tenet of Artificial Intelligence (AI) and cognitive science. But what kind of computation is cognition? We describe a computational formalism centered around a probabilistic Turing machine called QUERY, which captures the operation of probabilistic conditioning via conditional simulation. Through several examples and analyses, we demonstrate how the QUERY abstraction can be used to cast common-sense reasoning as probabilistic inference in a statistical model of our observations and the uncertain structure of the world that generated that experience. This formulation is a recent synthesis of several research programs in AI and cognitive science, but it also represents a surprising convergence of several of Turing’s pioneering insights in AI, the foundations of computation, and statistics.



Sequential Voronoi diagram calculations using simple chemical reactions

Por • 19 nov, 2012 • Category: Educacion

In our recent paper [de Lacy Costello et al. 2010] we described the formation of complex tessellations of the plane arising from the various reactions of metal salts with potassium ferricyanide and ferrocyanide loaded gels. In addition to producing colourful tessellations these reactions are naturally computing generalised Voronoi diagrams of the plane. The reactions reported previously were capable of the calculation of three distinct Voronoi diagrams of the plane. As diffusion coupled with a chemical reaction is responsible for the calculation then this is achieved in parallel. Thus an increase in the complexity of the data input does not utilise additional computational resource. Additional benefits of these chemical reactions is that a permanent record of the Voronoi diagram calculation (in the form of precipitate free bisectors) is achieved, so there is no requirement for further processing to extract the calculation results. Previously it was assumed that the permanence of the results was also a potential drawback which limited reusability. This paper presents new data which shows that sequential Voronoi diagram calculations can be performed on the same chemical substrate.



The Standard Aspect of Dialectical Logic

Por • 14 sep, 2011 • Category: Opinion

Dialectical logic is the logic of dialectical processes. The goal of dialectical logic is to introduce dynamic notions into logical computational systems. The fundamental notions of proposition and truth-value in standard logic are subsumed by the notions of process and flow in dialectical logic. Dialectical logic has a standard aspect, which can be defined in terms of the «local cartesian closure» of subtypes. The standard aspect of dialectical logic provides a natural program semantics which incorporates Hoare’s precondition/postcondition semantics and extends the standard Kripke semantics of dynamic logic. The goal of the standard aspect of dialectical logic is to unify the logic of small-scale and large-scale programming.



Some Remarks on the Value of Information from the Viewpoint of Aristotelian Semantic Triangle

Por • 11 sep, 2011 • Category: Opinion

The purpose of this paper is to make a conceptual analysis on the value of information from a philosophical point of view. In the paper, confining myself to a short philosophical comment, I take the following steps. (1) By referring to the Shannon’s classical paper on communication theory, I reconfirm one of the philosophically basic problems about the value of information, namely, the twisted relation between the elimination of meaning and our common-sense understanding of the value. (2) To elucidate the relation from a philosophical point of view, I take advantage of the Aristotle’s schematic overview called semantic triangle. The schema shows itself to have a systematic and wide-ranging conception. (3) Through analyzing the Aristotelian semantic triagle, I revaluate his philosophical insight that, in order to have a penetrating view of the value of information, we need more light on the value system from the viewpoint of human time, which is contrasted with physical or engineering time. What essentially matters is the relation between human time and Aristotelian common sense. (4) In temporary conclusion, I propose that to focuse attention on human time lead us to an adequate assessment on the crucial divide between quality and quantity in the value of information.



Toward a Generalized Theory of Uncertainty (GTU)—An Outline

Por • 4 sep, 2011 • Category: Crítica

It is a deep-seated tradition in science to view uncertainty as a province of probability theory. The Generalized Theory of Uncertainty (GTU) which is outlined in this paper breaks with this tradition and views uncertainty in a broader perspective. Uncertainty is an attribute of information. A fundamental premise of GTU is that information, whatever its form, may be represented as what is called a generalized constraint. The concept of a generalized constraint is the centerpiece of GTU. In GTU, a probabilistic constraint is viewed as a special—albeit important—instance of a generalized constraint.



The Harmonic Theory; A mathematical framework to build intelligent contextual and adaptive computing, cognition and sensory system

Por • 4 sep, 2011 • Category: Leyes

Harmonic theory provides a mathematical framework to describe the structure, behavior, evolution and emergence of harmonic systems. A harmonic system is context aware, contains elements that manifest characteristics either collaboratively or independently according to system’s expression and can interact with its environment. This theory provides a fresh way to analyze emergence and collaboration of «ad-hoc» and complex systems.