Continuous-time computation with restricted integration capabilities

AbstractRecursion theory on the reals, the analog counterpart of recursive function theory, is an approach to continuous-time computation inspired by the models of Classical Physics. In recursion theory on the reals, the discrete operations of standard recursion theory are replaced by operations on continuous functions such as composition and various forms of differential equations like indefinite integrals, linear differential equations and more general Cauchy problems. We define classes of real recursive functions in a manner similar to the standard recursion theory and we study their complexity. We prove both upper and lower bounds for several classes of real recursive functions, which lie inside the elementary functions, and can be characterized in terms of space complexity. In particular, we show that hierarchies of real recursive classes closed under restricted integration operations are related to the exponential space hierarchy. The results in this paper, combined with earlier results, suggest that there is a close connection between analog complexity classes and subrecursive classes, at least in the region between FLINSPACE and the primitive recursive functions

Proposta de um método para integração de conhecimento em classificação

Instituto Superior de Economia e Gestão.Os problemas considerados são problemas de classificação caracterizados por; 1) os objectos a classificar pertencem a uma de um conjunto de classes prédefinidas; 2) é conhecida a classificação de um conjunto de objectos (amostra); 3) todos os objectos são descritos por um conjunto de atributos. Esta categoria de problemas designa-se por problemas de classificação supervisada. Neste trabalho é proposto um método que permite tomar em consideração a informação incluída na amostra e conhecimento pericial sobre o domínio dos objectos a classificar. Os objectivos são: 1) definir uma regra de decisão para classificar a totalidade dos objectos; 2) tirar partido do conhecimento pericial para definir essa regra; 3) captar, em estruturas que descrevem o domínio dos objectos, o conhecimento envolvido no processo de classificação. A abordagem seguida consiste em desenvolver um método de classificação cujo suporte estrutural é uma árvore de decisão. O método auxilia, no decorrer do processo de classificação, o perito/decisor a formular hipóteses sobre o domínio dos objectos e permite estruturar e integrar o conhecimento pericial e a informação da amostra. O conhecimento resultante é incorporado em duas estruturas, uma árvore de classificação e um grafo bayesiano. O grafo bayesiano é um modelo qualitativo (gráfico) e quantitativo (probabilístico) de relações de causa-efeito entre as variáveis envolvidas. É apresentada uma implementação do método em C-PROLOG e uma aplicação a um problema real.N/

Prediction scenarios of past, present, and future environmental suitability for the Mediterranean species Arbutus unedo L.

Climate change is a challenge for forests in the coming decades, with a major impact on species adaptation and distribution. The Mediterranean Basin is one of the most vulnerable hotspots for biodiversity conservation under climate change in the world. This research aimed at studying a Mediterranean species well adapted to the region: the Arbutus unedo L. (strawberry tree). The MaxEnt, a presence-only species-distribution software, was used to model A. unedo’s environmental suitability. The current species potential distribution was accessed based on actual occurrences and selected environmental variables and subsequently projected for the Last Glacial Maximum (LGM), the Mid-Holocene (MH), and the years 2050 and 2070, considering the two Representative Concentration Pathways: RCP4.5 and RCP8.5. Results from the LGM projection suggest the presence of refugia in the core of the Mediterranean Basin, in particular the Iberian Peninsula (IP). The projections for the MH indicate increasing climatic suitability for the species and an eastward expansion, relatively to LGM. The predicted future environmental changes will most likely act as a catalyst for suitable habitat loss and a range shift towards the North is likely to occurinfo:eu-repo/semantics/publishedVersio

Continuous-time

computation with restricted integration capabilities a; b;

Upper and Lower Bounds on Continuous-Time Computation

We consider various extensions and modifications of Shannon's General Purpose Analog Computer, which is a model of computation by differential equations in continuous time. We show that several classical computation classes have natural analog counterparts, including the primitive recursive functions, the elementary functions, the levels of the Grzegorczyk hierarchy, and the arithmetical and analytical hierarchies