Sistema de accionamento de pás móveis para turbina de impulso

A actual dependência mundial dos combustíveis fósseis e a crescente necessidade de redução do seu consumo têm culminado em novas directrizes de gestão de recursos de energia. A utilização de recursos energéticos renováveis apresenta-se como um caminho vital para o desenvolvimento sustentável da nossa sociedade. Assim sendo, a energia das ondas surge como potencial fonte de energia que muitos autores afirmam como sendo um dos sectores com maior potencial energético por metro quadrado de área. Contudo, esta ainda é uma tecnologia muito recente, que ainda evidencia uma grande diversidade de conceitos e que ainda se encontra numa fase inicial de demonstração. É neste contexto que foi criado o projecto CORES que visa desenvolver uma turbina de impulso com pás guia de posição variável, no âmbito do desenvolvimento de novos dispositivos e componentes para produção de energia através das ondas do mar. Neste trabalho será desenvolvido um sistema de accionamento de pás móveis para a turbina de impulso, tendo como principal objectivo o fabrico de um protótipo. Assim sendo, será realizado o desenvolvimento, dimensionamento e análise dos seus elementos móveis, bem como do sistema de actuação que melhor se adeqúe e permita um correcto funcionamento do conjunto.

Amino acid in Deep Sea Drilling Project cores

Several amino acid diagenetic reactions, which take place in the deep-sea sedimentary environment, were investigated, using various Deep Sea Drilling Project (DSDP) cores. Initially it was found that essentially all the amino acids in sediments are bound in peptide linkages; but, with increasing age, the peptide bonds undergo slow hydrolysis that results in an increasingly larger fraction of amino acids in the free state. The hydrolysis half-life in calcareous sediments was estimated to be ~1-2 million years, while in non-carbonate sediment the hydrolysis rate may be considerably slower. The amino acid compositions and the extent of racemization of several amino acids were determined in various fractions isolated from the sediments. These analyses demonstrated that the mechanism, kinetics, and rate of amino acid diagenesis are highly dependent upon the physical state (i.e., free, bound, etc.) in which the amino acids exist in the sedimentary environment. In the free state, serine and threonine were found to decompose primarily by a dehydration reaction, while in the bound state (residue or HCl-insoluble fraction) a reversible aldol-cleavage reaction is the main decomposition pathway of these amino acids. The change in amino acid composition of the residue fraction with time was suggested to be due to the hydrolysis of peptide bonds, while in foraminiferal tests the compositional changes over geological time are the result of various decomposition reactions. Reversible first-order racemization kinetics are not observed for free amino acids in sediments. The explanation for these anomalous kinetics involves a complex reaction series which includes the hydrolysis of peptide bonds and the very rapid racemization of free amino acids. The racemization rates of free amino acids in sediments were found to be many orders of magnitude faster than those predicted from elevated temperature experiments using free amino acids in aqueous solution. The racemization rate enhancement of free amino acids in sediments may be due to the catalysis of the reaction by trace metals. Reversible first-order kinetics are followed for amino acids in the residue fraction isolated from sediments; the rate of racemization in this fraction is slower than that predicted for protein-bound amino acids. Various applications of amino acid diagenetic reactions are discussed. Racemization and the decomposition reaction of serine and threonine can both be used, with certain limitations, to make rough age estimates of deep-sea sediments back to several million years. The extent of racemization in foraminiferal tests which have been dated by some other independent technique can be used to estimate geothermal gradients, and thus heat flows, and to evaluate the bottom water temperature history in certain oceanic areas.

(Table 2, page 607) Composition of manganese nodules in cores from Leg 16, Deep Sea Drilling Project

Buried manganese nodules or encrustations were encountered at five drill sites of Leg 16. Surface nodules were also sampled at two sites. With few exceptions, nodules within any one drill hole are fairly uniform in composition and are similar in composition to samples obtained previously from the eastern equatorial Pacific. Geochemical and paleontological evidence suggests that at least one of the buried samples was in situ when found and that at least one other was not. The remaining nodules may have fallen from the sediment surface to the positions in which they were found during the drilling process.

O espaço do lazer infantil e as suas cores, formas e texturas

Given the high significance of playing on achildren's life, the existence of spaces for the same becomes essential. However, there are elements that should not be overlooked during its conception. In order for the space to become of the child, he must establish with it three relationships: with the space, with the objects in the room and with the other children. This article describes a part of the first empirical phase of an investigation. This phase of the project observed 14 children's play areas inserted in different environments, from the point of view of one of the main visual elements of design: colour. The aim is to understand which colours are the most used in the spaces and how the colour combination is performed. Thus, by crossing the observed colours and their meaning it is possible to determine what kind of space environments are intended to be created.

The DYMECS project: a statistical approach for the evaluation of convective storms in high-resolution NWP models

A new frontier in weather forecasting is emerging by operational forecast models now being run at convection-permitting resolutions at many national weather services. However, this is not a panacea; significant systematic errors remain in the character of convective storms and rainfall distributions. The DYMECS project (Dynamical and Microphysical Evolution of Convective Storms) is taking a fundamentally new approach to evaluate and improve such models: rather than relying on a limited number of cases, which may not be representative, we have gathered a large database of 3D storm structures on 40 convective days using the Chilbolton radar in southern England. We have related these structures to storm life-cycles derived by tracking features in the rainfall from the UK radar network, and compared them statistically to storm structures in the Met Office model, which we ran at horizontal grid length between 1.5 km and 100 m, including simulations with different subgrid mixing length. We also evaluated the scale and intensity of convective updrafts using a new radar technique. We find that the horizontal size of simulated convective storms and the updrafts within them is much too large at 1.5-km resolution, such that the convective mass flux of individual updrafts can be too large by an order of magnitude. The scale of precipitation cores and updrafts decreases steadily with decreasing grid lengths, as does the typical storm lifetime. The 200-m grid-length simulation with standard mixing length performs best over all diagnostics, although a greater mixing length improves the representation of deep convective storms.

Geochemical and radioactivity characterization of rocks from the Rio Preto (Go) Project

The Rio Preto Project, developed by the extinct Brazilian nuclear state company, Nuclebrás, during the late 70s and early 80s, consisted of basic geological mapping and radiometric characterization by aerogeophysical gamma-ray spectrometry, without channel discrimination, of a surface area of 650 km2 located to the west of the Chapada dos Veadeiros National Park on the northeastern of Goiás State, Brazil, including the confluence area of Claro and Preto Rivers. Additionally, the natural radioelements U, Th and 40K were determined by gamma-ray spectrometry in 300 rock samples from cores of the Rio Preto Project area. The tests were conducted at LABIDRO-Isotopes and Hydrochemistry Laboratory of the Departament of Petrology and Metallogeny (DPM) of the Institute of Geosciences and Exact Sciences, UNESP, in Rio Claro, SP, Brazil. This paper reports the results of petrographic characterization and chemical analyses of major oxides (SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, K2O, Na2O, CaO and P2O5) for all samples used to determine the natural radioelements present in the region. The organic matter content results obtained by colorimetry are also reported for selected cores of different lithotypes in order to investigate the possible relationship between graphite and the radioelements uranium and thorium. Finally, uranium content and 234U/238U activity ratio data for selected samples of schists and gneisses of the Lower Member of the Ticunzal Formation suggest the influence of weathering processes in the area. © 2012 Sociedade Brasileira de Geofísica.

Continuous Flow Analysis of labile iron in ice-cores

The important active and passive role of mineral dust aerosol in the climate and the global carbon cycle over the last glacial/interglacial cycles has been recognized. However, little data on the most important aeolian dust-derived biological micronutrient, iron (Fe), has so far been available from ice-cores from Greenland or Antarctica. Furthermore, Fe deposition reconstructions derived from the palaeoproxies particulate dust and calcium differ significantly from the Fe flux data available. The ability to measure high temporal resolution Fe data in polar ice-cores is crucial for the study of the timing and magnitude of relationships between geochemical events and biological responses in the open ocean. This work adapts an existing flow injection analysis (FIA) methodology for low-level trace Fe determinations with an existing glaciochemical analysis system, continuous flow analysis (CFA) of ice-cores. Fe-induced oxidation of N,N′-dimethyl-p-pheylenediamine (DPD) is used to quantify the biologically more important and easily leachable Fe fraction released in a controlled digestion step at pH ∼1.0. The developed method was successfully applied to the determination of labile Fe in ice-core samples collected from the Antarctic Byrd ice-core and the Greenland Ice-Core Project (GRIP) ice-core.

A technique for continuous detection of drill liquid in ice cores

When drilling ice cores deeper than ∼100 m, drill liquid is required to maintain ice-core quality and to limit borehole closure. Due to high-pressure air bubbles in the ice, the ice core can crack during drilling and core retrieval, typically at 600–1200 m depth in Greenland. Ice from this 'brittle zone' can be contaminated by drill liquid as it seeps through cracks into the core. Continuous flow analysis (CFA) systems are routinely used to analyse ice for chemical impurities, so the detection of drill liquid is important for validating accurate measurements and avoiding potential instrument damage. An optical detector was constructed to identify drill liquid in CFA tubing by ultraviolet absorption spectroscopy at a wavelength of 290 nm. The set-up was successfully field-tested in the frame of the NEEM ice-core drilling project in Greenland. A total of 27 cases of drill liquid contamination were identified during the analysis of 175 m of brittle zone ice. The analyses most strongly affected by drill liquid contamination include insoluble dust particles, electrolytic conductivity, ammonium, hydrogen peroxide and sulphate. This method may also be applied to other types of drill liquid used at other drill sites.

Lake Van deep drilling project PALEOVAN

A complete succession of the lacustrine sediment sequence deposited during the last ∼600,000 years in Lake Van, Eastern Anatolia (Turkey) was drilled in 2010 supported by the International Continental Scientific Drilling Program (ICDP). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. This introductory paper provides background information of the deep drilling project and an overview of the studies presented in this special volume by the PALEOVAN science team dealing with chronology, paleomagnetism, paleoenvironmental proxies, geophysical and petrophysical investigations as well as pore-water and fluid transport.

Geochemical and physical sediment properties of sediment cores from the Portuguese shelf

Marine sediments from the Portuguese shelf are influenced by environmental changes in the surrounding continental and marine environment. These are largely controlled by the North Atlantic Oscillation, but additional impacts may arise from episodic tsunamis. In order to investigate these influences, a high resolution multi-proxy study has been carried out on a 5.4 m long gravity core and five box cores from the Tagus prodelta on the western Portuguese margin, incorporating geochemical (Corg/Ntotal ratios, d13Corg, d15N, d18O, Corg and CaCO3 content) and physical sediment properties (magnetic susceptibility, grain-size). Subsurface data of the five box cores indicate no major effect of early postdepositional alteration. Surface data show a higher fraction of terrigenous organic material close to the river mouth and in the southern prodelta. Gravity core GeoB 8903 covers the last 3.2 kyrs with a temporal resolution of at least 0.1 cm/yr. Very high sedimentation rates between 69 and 140 cm core depth indicate a possible disturbance of the record by the AD1755 tsunami, although no evidence for a disturbance is observed in the data. Sea surface temperature and salinity on the prodelta, the local budget of marine NO3- as well as the provenance of organic matter remained virtually constant during the past 3.2 kyrs. A positive correlation between magnetic susceptibility (MS) and North Atlantic Oscillation (NAO) is evident for the past 250 years, coinciding with a negative correlation between mean grain-size and NAO. This is assigned to a constant riverine supply of fine material with high MS, which is diluted by the riverine input of a coarser, low-MS component during NAO negative, high-precipitation phases. End-member modelling of the lithic grain-size spectrum supports this, revealing a third, coarse lithic component. The high abundance of this coarse end-member prior to 2 kyr BP is interpreted as the result of stronger bottom currents, concentrating the coarse sediment fraction by winnowing. As continental climate was more arid prior to 2 kyr BP (Subboreal), the coarse end-member may also consist of dust from local sources. A decrease in grain-size and CaCO3 content after 2 kyr BP is interpreted as a result of decreasing wind strength. The onset of a fining trend and a further decrease in CaCO3 around AD900 occurs simultaneous to climatic variations, reconstructed from eastern North Atlantic records. A strong increase in MS between AD1400 and AD1500 indicates higher lithic terrigenous input, caused by deforestation in the hinterland.

Facies distribution in CRP sediment cores from the Ross Sea, Antarctica

Clasts from the Cape Roberts Project cores CRP-2/2A and CRP-3 provide indications of glacially influenced depositional environments in Oligocene and Miocene strata in the western Victoria Land Basin, Antarctica. CRP-2/2A is interpreted to represent strongly glacially influenced, unconformity bound depositional sequences produced by repeated advance and retreat of floating and grounded ice across the shelf. A similar interpretation is extended to the upper 330 meters of the CRP-3 core, but the lower part of the core records shallow marine deposition with significantly less glacial influence. Clast shape analysis from selected coarse-grained facies throughout the cored interval indicates that most clasts are glacially sourced, with little distinction between diamictite and conglomeratic facies. Three dimensional clast fabric analysis from units immediately above sequence boundaries generally display weak or random fabrics and do not suggest that grounded ice actually reached the drillsite at these intervals. Striated and outsized clasts present in fine-grained lithofacies throughout the cores provide further evidence of sub-glacially transported sediment and iceberg rafting. The distribution of these striated and out-sized clasts indicate that a significant glacial influence persisted through most of the time represented by the cores with glaciers actively calving at sea-level introducing ice-berg rafted glacial debris even in the earliest Oligocene.