890 resultados para phylogeography, consensus approach, ensemble modeling, Pleistocene, ENM, ecological niche modeling
Resumo:
We report in this work the study of the interaction between formic acid and an oxidized platinum surface under open circuit conditions. The investigation was carried out with the aid of in situ infrared spectroscopy, and results analyzed in terms of a mathematical model and numerical simulations. It has been found that during the first seconds of the interaction a small amount of CO(2) is produced and absolutely no adsorbed CO was observed. A sudden drop in potential then follows, which is accompanied by a steep increase first of CO(2) production and then by adsorbed CO. The steep transient was rationalized in terms of an autocatalytic production of free platinum sites which enhances the overall rate of reaction. Modeling and simulation showed nearly quantitative agreement with the experimental observations and provided further insight into some experimentally inaccessible variables such as surface free sites. Finally, based on the understanding provided from the combined experimental and theoretical approach, we discuss the general aspects influencing the open circuit transient.
Resumo:
Selective Estrogen Receptor Modulators ( SERMs) have been developed, but the selectivity towards the subtypes ( ER or ER is not well understood. Based on three-dimensional structural properties of ligand binding domains, a model that takes into account this aspect was developed via molecular interaction fields and consensus principal component analysis (GRID/CPCA).
Resumo:
This work aims at combining the Chaos theory postulates and Artificial Neural Networks classification and predictive capability, in the field of financial time series prediction. Chaos theory, provides valuable qualitative and quantitative tools to decide on the predictability of a chaotic system. Quantitative measurements based on Chaos theory, are used, to decide a-priori whether a time series, or a portion of a time series is predictable, while Chaos theory based qualitative tools are used to provide further observations and analysis on the predictability, in cases where measurements provide negative answers. Phase space reconstruction is achieved by time delay embedding resulting in multiple embedded vectors. The cognitive approach suggested, is inspired by the capability of some chartists to predict the direction of an index by looking at the price time series. Thus, in this work, the calculation of the embedding dimension and the separation, in Takens‘ embedding theorem for phase space reconstruction, is not limited to False Nearest Neighbor, Differential Entropy or other specific method, rather, this work is interested in all embedding dimensions and separations that are regarded as different ways of looking at a time series by different chartists, based on their expectations. Prior to the prediction, the embedded vectors of the phase space are classified with Fuzzy-ART, then, for each class a back propagation Neural Network is trained to predict the last element of each vector, whereas all previous elements of a vector are used as features.
Resumo:
A major problem in e-service development is the prioritization of the requirements of different stakeholders. The main stakeholders are governments and their citizens, all of whom have different and sometimes conflicting requirements. In this paper, the prioritization problem is addressed by combining a value-based approach with an illustration technique. This paper examines the following research question: How can multiple stakeholder requirements be illustrated from a value-based perspective in order to be prioritizable? We used an e-service development case taken from a Swedish municipality to elaborate on our approach. Our contributions are: 1) a model of the relevant domains for requirement prioritization for government, citizens, technology, finances and laws and regulations; and 2) a requirement fulfillment analysis tool (RFA) that consists of a requirement-goal-value matrix (RGV), and a calculation and illustration module (CIM). The model reduces cognitive load, helps developers to focus on value fulfillment in e-service development and supports them in the formulation of requirements. It also offers an input to public policy makers, should they aim to target values in the design of e-services.
Resumo:
In the past decade, compositional modelling (CM) has established itself as the predominant knowledge-based approach to construct mathematical (simulation) models automatically. Although it is mainly applied to physical systems, there is a growing interest in applying CM to other domains, such as ecological and socio-economic systems. Inspired by this observation, this paper presents a method for extending the conventional CM techniques to suit systems that are fundamentally presented by interacting populations of individuals instead of physical components or processes. The work supports building model repositories for such systems, especially in addressing the most critical outstanding issues of granularity and disaggregation in ecological systems modelling.