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A MOSFET only, step-up DC DC micro power converter, for solar energy harvesting applications

100%

Carvalho C. , Paulino N.

tom Vol. 1, nr 2

112-119

In this paper, a step-up micro power converter for solar energy harvesting applications is presented. The circuit is based on a switched-capacitor voltage doubler architecture with MOSFET capacitors, which results in an area approximately eight times smaller than using MiM capacitors for the 0.13 žm CMOS technology. In order to compensate for the loss of efficiency, due to the larger parasitic capacitances, a charge reutilization scheme is employed. The circuit uses a phase controller, designed specifically to work with the series of two PV cells, in order to regulate the output voltage to 1.2 V. Electrical simulations of the circuit, together with an equivalent electrical model of a PV cell, show that the circuit can deliver a power of 536.1 žW to the load, while drawing a power of 799.8 žW from two PV cells stacked in series, corresponding to a maximum efficiency of 67%.

Patterns of occurrence and distribution of crustacean ichnofossils in the Lower Jurassic-Upper Cretaceous of Atlantic occidental margin basins, Portugal

70%

Carvalho C. , Baucon A. , Rodrigues N. , Santos V. , Viegas P.

Acta Geologica Polonica

2010

tom Vol. 60, no. 1

19-28

Crustacean ichnofossils are most abundant in the stratigraphic record of Portugal. In this paper is presented a study on crustacean ichnoassemblages from the Sinemurian to middle Cenomanian, during the opening and subsequent filling of Atlantic occidental margin basins (Lusitanian Basin and western part of Algarve Basin). Thalassinoides dominates the lagoonal and inner shelf facies from the late Sinemurian at least to the Turonian, generally defining all of the carbonate sequence with its dense, "nodular" ichnofabric since the Late Jurassic. Asequence is described in the lower Barremian of Cabo Espichel in which burrow mazes of Thalassinoides suevicus occur, containing hundreds of Mecochirus rapax as an obrution lagerstatte. The Cretaceous of the Lusitanian Basin is rich in marly limestones mottled with Thalassinoides but almost devoid of Rhizocorallium. Fairly common in dark marls and biomicrites from the Jurassic, Rhizocorallium irregulare locally occurs in dense monospecific fabrics. Slipper-shaped and oblique forms (Rhizocorallium jenense) as well as spiral and lobate forms are rhizocoralliid foraging modifications usually developed in deeper tiers than Thalassinoides and sometimes evidencing bioimprints in Glossifungites preservation. Siliciclastic facies related to rifting subsidence along major fault scarps and fan deltas/braided river depositional systems show pervasive bioturbation with Psilonichnus tubiformis.Another crab-style behaviour ascribed to Macanopsis plataniformis is described for the first time in Portugal, associated with a coarse-grained sandstone episode in a tidal flat setting from the Kimmeridgian, where monospecific brachyuran burrows were developed in a firmground.