i-Rheo: determining the linear viscoelastic moduli of colloidal dispersions from step-stress measurements

We report on the application of a Fourier transform based method, `i-Rheo', to evaluate the linear viscoelastic moduli of hard-sphere colloidal dispersions, both in the fluid and glass states, from a direct analysis of raw step-stress (creep) experimental data. We corroborate the efficacy of i-Rheo by comparing the outputs of creep tests performed on homogenous complex fluids to conventional dynamic frequency sweeps. A similar approach is adopted for a number of colloidal suspensions over a broad range of volume fractions. For these systems, we test the limits of the method by varying the applied stress across the materials' linear and non-linear viscoelastic regimes, and we show that the best results are achieved for stress values close to the upper limit of the materials' linear viscoelastic regime; where the signal-to-noise ratio is at its highest and the non-linear phenomena have not appeared yet. We record that, the range of accessible frequencies is controlled at the higher end by the relative weight between the inertia of the instrument and the elasticity of the complex material under investigation; whereas, the lowest accessible frequency is dictated by the extent of the materials' linear viscoelastic regime. Nonetheless, despite these constrains, we confirm the effectiveness of i-Rheo for gaining valuable information on the materials' linear viscoelastic properties even from creep ringing data, confirming its potency and general validity as an accurate method for determining the material's rheological behaviour for a variety of complex systems

Miniaturised cylinder head production by rapid prototyping

This work shows the development of the design and manufacturing of a very small engine, namely its head. The engine works under the 4-stroke cycle, therefore having a very complex cylinder head, housing the camshaft, valves and its auxiliaries (seats, guides, springs), spark plug, inlet and exhaust passages and a coolant chamber. The geometries, both inner and outer are highly intricate which makes the production of such a part a very difficult job. In addition, when the engine is very small, as it is the case of this engine, all dimensions are miniaturized therefore making it extremely difficult to design, cast and finish. The cooling chamber, in particular, has a critical inner core removal problem due to reduced accessibility, imposing casting limitations. The cores place also a problem of air and gas removal during metal filling and solidification. Rapid prototyping may be the only solution to build the cores, and may help in the design and manufacturing phases of the casting tools. 3D printing with a plaster based material as a rapid prototyping technique presents itself as a tool to drastically reduce the design-development-casting process effort and time cycle. This technique enables the designer to obtain new moulds for castings on the shortest time possible, following redesign and new casting simulations. This paper illustrates the various tasks involved in the design and development stages leading to the production of a running prototype of the cylinder head for this small engine.Fundação para a Ciência e a Tecnologia (FCT) - POCI/EME/59186/2004, MIT-Pt/EDAM-SMS/0030/200

Morphophysiological Adaptations of \u3cem\u3eBrachiaria humidicola\u3c/em\u3e Cultivars under Grazing

Pastures of Brachiaria humidicola are broadly used in Brazil, especially in soils with low fertility and poor drain-age (Valle et al. 2010). Currently, 3 cultivars are commercially available: Tully, Llanero and BRS Tupi (available since 2012). Despite the extensive use of this species, research has focused primarily on aspects related to herbage and animal production, while only a few studies aimed at understanding morphological adaptations of the plants when subjected to grazing and contrasting environmental conditions. Therefore, the aim of this work was to evaluate some morphological traits of 2 B. humidicola cultivars when continuously stocked during 2 seasons of the year

Interaction of kinematic, kinetic, and energetic predictors of young swimmers’ speed

The aim of this study was to assess the interaction of kinematic, kinetic, and energetic variables as speed predictors in adolescent swimmers in the front-crawl stroke. Design: Ten boys (mean age [SD] = 16.4 [0.7] y) and 13 girls (mean age [SD] = 14.9 [0.9] y) were assessed. Methods: The swimming performance indicator was a 25-m sprint. A set of kinematic, kinetic (hydrodynamic and propulsion), and energetic variables was established as a key predictor of swimming performance. Multilevel software was used to model the maximum swimming speed. Results: The final model identified time (estimate = −0.008, P = .044), stroke frequency (estimate = 0.718, P < .001), active drag coefficient (estimate = −0.330, P = .004), lactate concentration (estimate = 0.019, P < .001), and critical speed (estimate = −0.150, P = .035) as significant predictors. Therefore, the interaction of kinematic, hydrodynamic, and energetic variables seems to be the main predictor of speed in adolescent swimmers. Conclusions: Coaches and practitioners should be aware that improvements in isolated variables may not translate into faster swimming speed. A multilevel evaluation may be required for a more effective assessment of the prediction of swimming speed based on several key variables rather than a single analysisThis work is supported by national funds (FCT–Portuguese Foundation for Science and Technology) under the project UIDB/DTP/04045/2020.info:eu-repo/semantics/publishedVersio

Tillering Dynamics of \u3ci\u3ePanicum maximum\u3c/i\u3e Jacq. cv. Tanzania-1 After Grazing

Tillering dynamics and tiller dry matter weight from Tanzania grass (Panicum maximum cv. Tanzania-1) were evaluated in two post-grazing stubbles (High Post-grazing Stubble – HPS-3.6 t of DM/ha and Low Post-grazing Stubble – LPS-2.3 t of DM/ha). There was no difference between post-grazing stubbles for decapitated axillary and basal remainder and new axillary tillers. The LPS presented greater number of new basal tillers. The rate of appearance of new basal and axillary tillers decreased with time after grazing. There were differences between the treatments on tiller dry matter weight, and greater values were found in the high post-graze stubble

Qualidade em agricultura: sistemas de certificação, desafios e perspectivas

Qualidade, quando referida ao sector agrícola, integra toda a cadeia produtiva, desde a provisão de matérias-primas até ao consumo e pode ser vista na óptica do produtor e do consumidor. Os sistemas de garantia e certificação da qualidade existentes na União Europeia, baseados numa abordagem holística, são particularmente complexos e variados, pela diversidade de consumidores existentes. A maioria aplica-se a um mercado diferenciado e apenas um reduzido número e muito diversificado vai além das normas legais, visando a diferenciação dos produtos e a manutenção de determinados padrões de qualidade. O seu desenvolvimento é influenciado por medidas de políticas distintas e, factores económicos e sociodemográficos. Podem classificar- se em função do objecto (produtos ou processos), dos objectivos (consumidor final ou os diferentes intervenientes na cadeia de comercialização alimentar), o conteúdo (rastreabilidade na origem ou modo de produção), os promotores (públicos ou privados), o contexto (local, regional, nacional ou internacional) e, o número de etapas envolvidas na cadeia agro-alimentar

Herbage Production of Tanzania Grass (\u3cem\u3ePanicum maximum\u3c/em\u3e cv. Tanzania) Submitted to Combinations of Frequencies and Intensities of Grazing by Cattle

Animal production from pastures is a complex process comprising three main stages: herbage growth, consumption by grazing animals and conversion into animal products (Hodgson, 1990). Utilisation is the stage where the grazier finds greater flexibility for management, probably because most processes related to harvest of the produced herbage by the grazing animals are very responsive to manipulation and control of defoliation practices. The objective of this study was to evaluate herbage production of a Panicum maximum cv. Tanzania pasture submitted to combinations of frequencies and intensities of grazing

Complete loop quantization of a dimension 1+2 Lorentzian gravity theory

De Sitter Chern-Simons gravity in D = 1 + 2 spacetime is known to possess an extension with a Barbero-Immirzi like parameter. We find a partial gauge fixing which leaves a compact residual gauge group, namely SU(2). The compacticity of the residual gauge group opens the way to the usual LQG quantization techniques. We recall the exemple of the LQG quantization of SU(2) CS theory with cylindrical space topology, which thus provides a complete LQG of a Lorentzian gravity model in 3-dimensional space-time.Comment: Loops11 - Madrid - 2011 (4 pages, Latex

Analysis of csp-1 under infallible and fallible inspection systems

In this paper, we discuss the implementation of Continuous Sampling Plan (CSP)-1 under two scenarios: (i) infallible, and (ii) fallible inspection systems. For both cases, we develop an optimization model for designing a CSP-1 that minimizes the total expected cost. We use Markov theory to derive the expected results from the application of the CSP-1. A Bayesian approach is used to model the inspection system reliability. Based on the analyses for the two models, we offer a discussion on the adverse effects of disregarding inspection errors when implementing CSP-1