The study of sedimentological features, foraminifera and molluscan fauna in samples recovered from four rotary boreholes permitted, after 14C dating, the first assessment of the post-glacial transgression in Guadiana River Estuary. The Holocene sequence is underlain by coarse sediments from delta fan enclosing continental swamp deposits dated 16 980 year BP. The Holocene sedimentary sequence was deposited either directly on this delta fan gravels or on top of fluvial sands deposited probably between 11 000 and 10 000 yr BP. An accelerated phase of the estuary infilling by clayey sediments containing the salt marsh foraminifer Trochammina, began ca. 9800 year BP, when sea level was about 39 m below present. Between 7500 and 7000 year BP, the central part of the estuary started to accommodate coarser sediments, partially introduced from the continental shelf. The first phase of Holocene sea-level rise at a rate of 0.85 m/century terminated ca. 6500 year BP. Since then, lagoonal sediments in the vicinity of the estuary have been enclosed behind sand spits and predominantly sandy sedimentation was initiated within the estuary. After a second phase of slower rise at the rate of 0.3 m/century, which lasted until ca. 5000 year BP, the sea approached the present level.

While some leakage power reduction techniques require modification of process technology achieving savings at the fabrication stage, others are based on circuit-level optimizations and are applied at run-time. We focus our study on the latter kind and compare three techniques: Input Vector Control, Body Bias Control and Power Supply Gating. We determine their limits and benefits, in terms of the potential leakage reduction, performance penalty and area and power overhead. The importance of the 'minimum idle time' parameter, as an additional evaluation tool, is emphasized, as well as the feasibility of achieving Power Supply Gating at low levels of granularity. The obtained data supports the formulation of a comprehensive leakage reduction scheme, in which each technique is targeted for certain types of functional units and a given level of granularity depending on the incurred overhead cost and the obtainable savings.

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