261 research outputs found
An integrated framework for regional studies: Emergy based spatial analysis of the Province of Cagliari
No full textThis research proposes an integrated framework to investigate human-dominated systems and provide a basic approach to urban and regional studies in which the multiple interactions between economic and ecological processes are considered as a whole. Humans generate patterns of land use, infrastructures and other settings and redistribute ecosystem functions as flows of energy and matter for self-maintenance. To understand these emerging interactions between humans and ecological processes, human activities (e.g. transformation processes, land conversions, use of resources) and biophysical agents such as geomorphology, climate and natural cycles need to be considered. Emergy Analysis (spelled with an "m") is then used as an environmental accounting method to evaluate different categories of resource use with reference to their environmental cost. A case study of the Province of Cagliari (in the island of Sardinia, Italy) is reported and the procedure for allocating emergy flows, assigning them to districts and managing point data is discussed. Outcomes plotted on a map showed non-homogeneous spatial distribution of emergy flows throughout the region, suggesting the way ecosystem functions are affected and restructured by the human economy
Effect of medium viscosity in a closed unstirred Belousov-Zhabotinsky system
No full textComplex periodic and aperiodic behaviors are reported in an unstirred Belousov–Zhabotinsky oscillatory reaction
containing different concentrations of polyethylene-glycol. A route from chaos following an inverse Ruelle–Takens–New-
house RTN. scenario is identified. Thus, hydrodynamic effects, being mainly convective, seem to be responsible for the
observed RTN scenario. We demonstrate that the medium viscosity, namely the polyethylene-glycol concentration, is a
bifurcation parameter for the sequence chaos --> quasi-periodicity --> period-1. reserved
Gli strati materici del gruppo del Rustici: indagini analitiche e loro implicazioni
No full textNell'ambito dell'intervento di restauro del gruppo scultoreo in bronzo della “Predica del Battista” di Giovanfrancesco Rustici sono state effettuate indagini scientifiche finalizzate a raccogliere elementi conoscitivi sull'opera e funzionali allo stesso intervento di restauro.
E' stato innanzi tutto eseguito un approfondito esame obiettivo delle superfici sia interne che esterne delle statue costituenti il gruppo scultoreo. E' stata quindi effettuata una caratterizzazione microstratigrafica delle patine presenti sulle superfici esterne, indicative sia di fenomeni di degrado che di applicazioni intenzionali (scialbi e bronzature). Sono state caratterizzate le leghe e le anime di fusione sul piano mineralogico-petrografico e geochimico.
L'insieme delle indagini svolte ha permesso di mettere in luce aspetti precedentemente non noti riguardanti la tecnica di realizzazione dell'opera e i restauri della medesima nel corso dei secoli
Coupling of erratic Belousov-Zabotinsky oscillators observed by spectrophotometric measure
No full textIsotopic Effect on the Kinetics of the Belousov-Zhabotinsky Reaction
Get PDFIn this work we present results about the deuterium isotope effect on the global kinetics of a Belousov-Zhabotinsky reaction in batch conditions. A nonlinear dependence of the Induction Period upon the percentage of deuterated reactants was found. The isotopic effect on the bromination reaction of malonic acid was evaluated
Recurrence quantification analysis of spatio-temporal chaotic transient in a closed unstirred Belousov-Zhabotinsky reaction
Get PDFWe analyse the transient spatio-temporal chaos that we observe in the Belousov-Zhabotinsky reaction performed in a closed unstirred batch reactor by recurrence quantification analysis (RQA). We characterize the chaotic transient by measuring the Lyapunov exponent and the Kaplan-Yorke dimension. The latter shows the fractality of the attractor. The importance of the coupling between hydrodynamics and kinetics for the onset of chaos is also shown
Exploring Gas Evolution Oscillators: Mechanisms and Applications
No full textWe review an iconic class of chemical oscillators driven by phase transition instabilities, namely Gas Evolution Oscillators (GEOs). These systems show oscillatory dynamics in the delivery of gas sustained simple reactions yielding gaseous products in a liquid mixture, due to nucleation and supersaturation phenomena. After presenting the main features and properties of these systems, we deepen the underlying mechanism through a unified picture of the various models that have been proposed to describe this kind of oscillations. We finally discuss a concrete example of how such instabilities can impact chemical processes with applied relevance
Exergy versus emergy flow in ecosystems: is there an order in maximizations?
No full textFrom ecosystems theory, orientors have been derived to give a holistic view of the trend of development of ecosystems themselves. Several principles of maximization, mainly derived from Lotka's maximum power, are connected with these orientors. Other authors (Jørgensen, Patten and coworkers, for example) have shown that among these orientors there are many common aspects, both form a quantitative terms and in principle. We show how H.T. Odum's maximum empower and Jørgensen's maximum exergy principles can be both valid from a practical viewpoint. As suggested by a simple experiment there can be a time order: first the maximization of empower and then the maximization of exergy. This time sequence is also consistent with a maximization trend in the ratio of exergy to empower. © 2005 Elsevier Ltd. All rights reserved
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