A comparison between the stresses computed for finite sized precast concrete pavement units using westergaards equations and a numerical design method

Westergaards equations are widely used in the design of rigid concrete highway and aircraft pavements. The equations assume that the pavements are either infinite or semi-infinite in extent. Recently, a numerical design procedure using finite elements has been introduced for finite sized precast concrete pavement units [raft units]. The present paper compares the computed stress results from the two methods for the interior loading on a two metre square raft unit. The results show that there is no simple “slab-size correction factor” to correlate the stress output from the two design methods as suggested by other authors. Westergaards analysis should not be used to design finite sized raft units; the numerical design procedure is recommended.     

Mutual Potential of Homogeneous Polyhedra

The mutual gravitational potential between a pair of homogeneous polyhedra is expressed using an infinite series. The nested volume integrals are evaluated analytically and result in simple tensor expressions containing no special functions. However, complexity increases as O(6 ⁿ ), where n is the term degree. An alternate formulation due to Liebenthal is also presented.     

Northern Ireland lignite

Conclusion There is no doubt that Northern Ireland's lignite deposits are of high quality and constitute a natural resource of considerable potential value in this small, peripheral part of the European Community. Whether or not one or more will be used commercially and, if so, when depends on an interacting complex of economic, social and political factors. In purely economic terms, use will be effectively determined by lignite's economic competitiveness as a fuel dor electricity generation and on the relationship between capital and fuel costs. The economics of other possibly viable products such as lignite briquettes will be heavily dependent on the use of by-products of electricity generation, most notably surplus heat.The availability of lignite offers an alternative fuel option to those charged with formulating the Province's energy policy. If, as now seems likely, it is no longer a serious competitor for the power station planned for the mid-1990's, it most certainly is a competitor for the early part of the next century. This is particularly so in view of its low sulphur content which is about half that of Scottish coal on an energy equivalent basis. Lignite also offers security of supply at predictable prices, an important advantage, and thus carries a premium over coal, oil and natural gas which are imported at prices determined wholly exogenously.As the Province has by far the highest rate of regional unemployment in the United Kingdom, one argument advanced for the use of indigenous lignite is that its use in electricity generation would create much needed additional employment — an estimated 400 jobs being associated with the mining operations needed to support a 450 MW power station. But the Coagh example shows that other considerations must be taken seriously. It is extremely unlikely that the lignite in this area will ever be worked unless local attitudes change dramatically or there is some national fuel crisis which would over-ride local opposition. It is difficult enough developing lignite without having to contend with such strong resistance at the local level.This study has shown that certainly in the Northern Irish context it is highly important for the policy makers not only to consider the economic factors involved in choice of an energy fuel but to work closely with local communities and the various environmental bodies, to take their perceptions, right or wrong, into consideration.     

Long-distance traffic routes to and from Berlin

After the reunification of Germany on October, 3rd. 1990 Berlin becam a unified city again. Most of the ambitious plans of the pre-war time concerning the urban infrastructure could not be taken up again after fourty years of division. The article describes the long-distance traffic system in the former capital of the Reich, the division and duplication of the transportation facilities in the decades of division and gives an overview of concepts of reconstruction and new plans for the reunited Berlin and its hinterland.     

The myth of the brackish Sarmatian Sea

The biota of the 1.5 Ma period of the Middle Miocene Sarmatian of the Central Paratethys lack stenohaline components. This was the reason to interpret the Sarmatian stage as transitional between the marine Badenian and the lacustrine Pannonian stages. However, our new data indicate that brackish water conditions could not have prevailed. Sarmatian foraminifera, molluscs, serpulids, bryozoans, dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire Sarmatian. During the Lower Sarmatian, however, a sea-level lowstand forced the development of many marginal marine environments. During the Late Sarmatian a highly productive carbonate factory of oolite shoals, mass-occurrences of thick-shelled molluscs and larger foraminifera, as well as marine cements clearly point to normal marine to hypersaline conditions. This trend is not restricted to the western margin of the Pannonian Basin System but can be observed in the entire Central and even Eastern Paratethys.     

Karrenbilder

Ohne Zusammenfassung