Landsat TM analysis of fracture patterns: a case study from the Coastal Cordillera of northern Chile

Cretaceous rocks on the continental margin of northern Chile record a complex geodynamic evolution. Cycles of transtensional and transpressional deformation and of extrusive and intrusive magmatism are linked to the development of crustal-scale lineaments. The Landsat Thematic Mapper is used here as a tool to define these structural features. Geocorrected data were digitally enhanced and lineaments plotted directly from a hard copy image, thereby excluding artificial or non-geological features that might degrade the subsequent structural analysis. The lineaments were then digitized and analysed using a Weighted Moving Average (WMA) technique to suppress noise and to enhance azimuthal variation. Statistical analysis of the data reveals three lineament populations. The first is a set of NNE-trending lineaments that belong to the margin-parallel, sinistral Atacama Fault System. The second is a series of NW-trending lineaments with a similar orientation to large-scale structures identified across the South American continental plate. The third is a widely spaced set of NE-trending lineaments. The key result of this study is that lineaments identified from remotely sensed data may have orientation patterns that differ considerably from those identified by traditional geological mapping and that full structural analysis of structurally complex crustal regions will likely be incomplete without a comprehensive analysis of remotely sensed data. Although the NW-trending structures are numerically dominant on the Landsat TM image, they are seldom recorded at map scale and are under-represented on published geological maps. Of the 275 faults marked on the published geological map sheets, 89 are N to NNE-trending and only 88 are NW-trending. By contrast, of 841 lineaments identified from the satellite image, 455 are NW-trending and 178 are N- to NNE-trending. The lack of prior recognition of the NW-trending structures means that their importance has been underestimated in reconstructions of the geodynamic evolution of the region. In addition, as major ore deposits in the region are frequently located at intersections between two fracture systems, the recognition here of the NW-trending set of structures should illuminate future mineral exploration programmes.     

Theoretical Investigation of the Size Effect on the Oxygen Adsorption Energy of Coinage Metal Nanoparticles

Catalysis Letters - This study evaluates the finite size effect on the oxygen adsorption energy of coinage metal (Cu, Ag and Au) cuboctahedral nanoparticles in the size range of 13 to 1415 atoms...     

Simulations in Coalgebra

A new approach to simulations is proposed within the theory of coalgebras by taking a notion of order on a functor as primitive. Such an order forms a basic building block for a “lax relation lifting”, or “relator” as used by other authors. Simulations appear as coalgebras of this lifted functor, and similarity as greatest simulation. Two-way similarity is then similarity in both directions. In general, it is different from bisimilarity (in the usual coalgebraic sense), but a sufficient condition is formulated (and illustrated) to ensure that bisimilarity and two-way similarity coincide. Also, a distributive law is identified which ensures that similarity on a final coalgebra forms a dcpo structure.     

AN EVALUATION OF THE ECONOMICS OF FUEL CELLS IN URBAN BUSES

One of the contenders for a clean source of on-board electric power in a vehicle is the fuel cell: an electrochemical device that transforms the chemical energy stored in a fuel directly into electricity. While less widely known and less far advanced than batteries, fuel cells hold a considerable potential to provide the power for a novel generation of non-polluting vehicles. At present, fuel cell technology is entering the stage of commercialization, which is an appropriate moment to try and assess its economic potential in the field of transport. Based on a review of the present state of the technology, concentrating on the solid polymer fuel cell, a model is set up of a fleet of urban buses, widely regarded as one of the earliest applications of fuel cells in transport. Under the central assumption that the fuel cell stack cost is $300 per kilowatt, the fuel cell bus is found to be around 30% more expensive than its diesel counterpart. However, there are considerable cost reductions possible through economies of scale in the production of hydrogen, the fuel required for the solid polymer fuel cell. Remarkably, these economies of scale allow the cost of the fuel cell bus to drop below that of the diesel. What is more, the fleet size required for this—more than 25 vehicles—is by no means prohibitive. In a trade-off analysis, the possibility is investigated of reducing the cost by allowing one parameter to deteriorate, if this permits another one to improve. In particular, it is found that cheaper (mass-) production techniques for the fuel cell at the expense of reduced efficiency make economic sense if a relative drop in the efficiency of 1% is accompanied by a cost reduction of at least 1⋅06%—something that is likely to be attainable. A scenario for a direct methanol fuel cell, assuming a cost per kilowatt three times as high as for the solid polymer fuel cell, results in a slightly higher overall cost, without being able to offer the same economies of scale in fuel provision. The social costs are calculated also, taking into account the environmental externalities associated with the whole system including the fuel supply chain. The inclusion of externalities fails to shift the balance decisively in favour of the fuel cell, partly because of a cancellation effect between the diesel tax, which has to be excluded in a social cost calculation, and the externalities, which are added in. The main outcome is therefore that in order to succeed in the marketplace, the principal task for the developers of fuel cells is a further reduction of the cost. © 1997 by John Wiley & Sons, Ltd.     

Electrostatic Drop Formation in Liquid/Liquid Systems

Electrostatic drop formation in liquid/liquid systems was studied, using high frequency AC fields (45 kHz). The dispersion of nonconductive into conductive fluids was investigated under various conditions, as are the effect of aqueous phase conductivity, capillary geometry and organic phase viscosity on the resulting drop size. The experimentally determined drop sizes and literature data, were correlated with a model equation, which was derived from a simple force balance, with an empirical term for the electric force. The model parameters were obtained in a toluene/water system and the model allows the prediction of the drop sizes of other organic solvents, if the capillary geometry is kept constant.