Search

When it comes to testing ECUs for vehicle dynamics systems, Hardware-in-the-Loop (HiL) testing systems make a valuable contribution. All tests can be executed automatically and with real-time reference - with the benefit of accurate reproducibility - in a manner that exposes neither driver nor test vehicle to any hazards whatsoever. The rapid acceleration of system complexity in this area also affects the HiL system. As a result, the conventional approach of visualizing the simulation model and the real-time tests in a single monolithic block is beginning to test its very limits. Novel concepts, such as the separation into modules and plugins discussed below, are realizing decisive benefits not only to driving dynamics systems.

Bei Steuergeratetests von Fahrdynamiksystemen leisten Hardware-in-the-Loop (HiL)-Testsysteme einen wertvollen Beitrag. Alle Tests konnen exakt reproduzierbar, automatisiert und mit Echtzeit- Bezug durchgefuhrt werden, ohne dass Fahrer und Fahrzeug gefahrdet werden. Die rasante Zunahme der Systemkomplexitat in diesem Bereich hat auch Auswirkungen auf das HiL-System. So stost das konventionelle Vorgehen, das Simulations modell und die Echtzeit-Tests in einem monolithischen Block darzustellen, immer mehr an seine Grenzen. Neue Konzepte, wie die hier von Etas vorgestellte Trennung in Module und Plug-ins bringen nicht nur fur Fahrdynamiksysteme entscheidende Vorteile.

Published major-element analyses of Ethiopian volcanic rocks have been subjected to a systematic discriminant analysis. The plateau regions can be subdivided according to the proportions of alkaline and tholeiitic basalts. In northern Ethiopia, these subprovinces show increasing basalt alkalinity with time. The most voluminous basalts have lowest magnesium values, independent of the degree of alkalinity. Rift and Afar basalt chemistry falls within the spectrum observed for the plateau basalts, with no perceptible difference resulting from lithospheric attenuation beneath Afar. However, silicic volcanics of the Rift-Afar floor differ in bulk terms from those of the plateau margins in showing a stronger bias towards peralkalinity, and having higher Na/K values. Two particularly voluminous volcanic episodes have occurred in Ethiopia, dated at ?30–19 m.y. and 4.5–0 m.y. and which link well with one model for seafloor spreading in the Red Sea and Gulf of Aden. Evidence for a mantle hotspot under Ethiopia remains ambiguous.

A general riftward younging of surficial volcanic units is a feature of the Addis Ababa sector of the Ethiopian rift valley. The narrowing of the volcanic zone with time is due to crustal necking and topographical control.

The most voluminous outpourings of lava on the land surface of the Earth have built imposing stacks of superimposed basalt flows, as much as several thousands of metres thick. Such stacks, or piles, were fed from linear zones of fracturing and fissuring in the crust through which basaltic magma emerged in successive pulses, flooding out over the surrounding region for distances as far as a few hundred kilometres. The fluid nature of these ‘flood basalt’ lavas resulted in the formation of a subdued or planar new topography which, when uplifted during subsequent tectonic episodes, has produced what are popularly termed ‘volcanic plateaus’.

O’a is the largest of the Quaternary caldera volcanoes that punctuate the axis of the Ethiopian rift valley. The known volcanic history of O’a is brief: eruptions of restricted ash-flow tuffs and «tufolavas» were followed by extensive pumice deposition with intervening paleosols, lacustrine sediments, and flows of occasional welded tuffs and rare basalts. Ensuing caldera collapse at c. 0.24 m.y. ago was accompanied by emplacement of two massive ignimbrite flow units comprising a single cooling unit: the first was much more severely welded than the second which shows lahar characteristics. Post-caldera volcanism at O’a has been sparse compared with most other Ethiopian rift centres. O’a volcano exemplifies the common rift association of a caldera set tightly between two offset segments of the Wonji fault belt. The Wonji fault belt marks the youngest tectonism of the rift floor, and in the vicinity of O’a has been active in a major way since caldera subsidence. This faulting is clearly younger than the massive rift margin faulting, which to the northeast of O’a occurred during a tectonic climax dated at c. 1.0 m.y. ago. Radiometric analysis suggests a rather regular level of initial40Ar in O’a basalt lavas sampled near to their original vents. If this level also applies to near-vent basalts dated from other parts of the Ethiopian rift, a regional rift paroxysm of crustal extension and related silicic and basaltic volcanism is evident at c. 0.30–0.20 m.y. ago. Episodic dilatation and associated volcano-tectonism separated by long periods of quiescence appears to be a general feature of continental rift valleys.

THE African rift system is usually considered to be a continental extension of the mid-oceanic ridge–rift system, a connexion being made through the Gulf of Aden and the Gulf of Tajura. The detailed connecting pattern, complicated by the convergence of the Red Sea structures, shows that in terms of seismic epicentre distribution (unpublished work of P. Gouin), volcanism1 and crustal tectonics2 the transition from oceanic to continental rift is not made as smoothly as many previous hypotheses supposed.

The discovery of extensive Pliocene pantellerite welded tuffs in southern Ethiopia necessitates a revision of the Cainozoic volcanic succession associated with the Ethiopian rift system.

THE almost random occurrence of earthquakes seems to rule out any useful method of forecasting, at least until we understand and can closely monitor earth mantle processes. The probable influence of known natural factors like earth and ocean tides in triggering earthquakes is not sufficiently determining to be a forecasting aid. More hopeful are the results of ground deformation monitoring in the vicinity of such fault zones as the San Andreas, where patterns are emerging between ground deformation and ensuing local earthquakes1.

RECENT exploration and field-work in Ethiopia, in particular gravity–geology surveys made by Prof. P. Gouin, Dr. A. S. Rogers and me, have shown the Cainozoic volcanic succession in association with the Ethiopian Rift System to be more complicated than previously suspected.

MCKENZIE et al.1 have produced a strong case for considering the East African rifts and the Afar triple junction in terms of oceanic plate tectonics. I should like to present some arguments suggesting that modification to plate analysis of continental regions is required, for tensional as well as for compressional zones2.

Geology Today. Editor-in-chief. John H. McD. Whitaker. Blackwell Scientific. 6/yr. UK £45.50, North America and Japan $87.50, elsewhere £54.50 (institutional); UK £15, North America and Jap an $28.50, elsewhere £18 (individual).