A Search for Fluctuation-Dissipation Theorem Violations in Spin-Glasses from Susceptibility Data

We propose an indirect way of studying the fluctuation-dissipation relation in spin-glasses that only uses available susceptibility data. It is based on a dynamic extension of the Parisi-Toulouse approximation and a Curie-Weiss treatment of the average magnetic couplings. We present the results of the analysis of several sets of experimental data obtained from various samples.Comment: 7 pages, 4 figure

Efeito da solarização na população infestante de tiririca (Cyperus rotundus) e na produção de hortaliças.

bitstream/CNPAB-2010/27143/1/cot018.pd

Utilização de minhocas na estabilização de resíduos orgânicos: Vermicompostagem.

Criação das minhocas.bitstream/CNPAB-2010/27133/1/cot008.pdfed. rev. mod

Measuring performance in agri‐food supply chains: A case study of a Portuguese company

Organizations seek to create value, increase competitiveness, reduce costs, share information and strengthen relationships between the various actors in the chain. In this sense, it is of the utmost importance that tools be developed which define objectives, monitor processes and document the performance of the supply chains. The Performance Measurement Systems (PMS) have come about to aid decision support, bringing together relevant Key Performance Indicators (KPis) which are fundamental for decision makers when deciding the best strategies for increasing supply chain competitiveness. In this study a PMS was developed collating a range of KPIs that seek to help in the continuous improvement of the agri-food supply chain. A case study allowed a PMS model to be designed incorporating the experiences of professionals in the area and subsequent tests to be made of its applicability, its outputs and its usefulness for decision support in a Portuguese plant.info:eu-repo/semantics/publishedVersio

On composite systems of dilute and dense couplings

Composite systems, where couplings are of two types, a combination of strong dilute and weak dense couplings of Ising spins, are examined through the replica method. The dilute and dense parts are considered to have independent canonical disordered or uniform bond distributions; mixing the models by variation of a parameter $\gamma$ alongside inverse temperature $\beta$ we analyse the respective thermodynamic solutions. We describe the variation in high temperature transitions as mixing occurs; in the vicinity of these transitions we exactly analyse the competing effects of the dense and sparse models. By using the replica symmetric ansatz and population dynamics we described the low temperature behaviour of mixed systems.Comment: 35 pages, 9 figures, submitted to JPhys

Numerical investigation of AC arc ignition on cold electrodes in atmospheric-pressure argon

Since experiments cannot clarify the mechanism of current transfer to non-thermionic arc cathodes, this can only be done by means of numerical modelling based on first principles and not relying on a priori assumptions. In this work, the first quarter-period after the ignition of an AC arc on cold electrodes in atmospheric-pressure argon is investigated by means of unified one-dimensional modelling, where the conservation and transport equations for all plasma species, the electron and heavy-particle energy equations, and the Poisson equation are solved in the whole interelectrode gap up to the electrode surfaces. Results are compared with those for DC discharges and analysed with the aim to clarify the role of different mechanisms of current transfer to non-thermionic arc cathodes. It is found that the glow-to-arc transition in the AC case occurs in a way substantially different from the quasi-stationary glow-to-arc transition. The dominant mechanisms of current transfer to the cathode during the AC arc ignition on cold electrodes are, subsequently, the displacement current, the ion current, and thermionic emission current. No indications of explosive emission are found. Electron emission from the impact of excited atoms can hardly be a dominant mechanism either. The introduction of the so-called field enhancement factor, which is used for description of field electron emission from cold cathodes in a vacuum, leads to computed cathode surface temperature values that are appreciably lower than the melting temperature of tungsten even in the quasi-stationary case. This means that pure tungsten cathodes of atmospheric-pressure argon arcs can operate without melting, in contradiction with experiments.info:eu-repo/semantics/publishedVersio