Desertification,famine, and the 1988 rainfall —     

Prof. Dr. Mustafa M. Khogali 《GeoJournal》1991,25(1):81-89

The 1988 good rainy season in the Sudan raised the hopes that desertification/land degradation and shortage of food so markedly observed in Western Sudan have been elevated. This was particularly so as large quantities of grains were produced in the mechanized rain-fed agricultural schemes in the clay plains of Eastern Sudan. But the field work carried by the author in the Umm Ruwaba district of Kordofan region in July/August 1989 shows that, although there has been some improvement in the crop production situation, desertification/land degradation and shortage of food produced locally are still prevailing in the district. The people are still living below the poverty line, but they are able to cope because of remittances from members of the families working abroad and because of donations of food by some world organizations.  相似文献   

Stress-strain fields at the tunnelling face—Three-dimensional analysis for two-dimensional technical approach     

S. Kielbassa  Prof. Dr.-Ing. H. Duddeck 《Rock Mechanics and Rock Engineering》1991,24(3):115-132

Summary For tunnelling in rock, the original stress field in the ground is changed considerably before a first lining is participating in stabilizing the opening. Depending on this stress release at the tunnel face, only a small portion of the primary stresses is acting on the lining. Only a three-dimensional approach is able to determine the stresses and the deformations of the ground and the lining realistically. The paper presents some results of elastic three-dimensional finite-element-analyses in consecutive steps of the sectional excavation of circular and non-circular tunnels. From these results an equivalent two-dimensional approach is derived for technical applications, given in diagrams.  相似文献   

A method for constructing toxic waste site histories from old airphotos of coastal regions     

Glen C. Gustafson Dr. 《GeoJournal》1991,24(1):87-91

Archive aerial photos have been used to create a skeletal history for several toxic waste sites currently under investigation in the United States. Because many of the sites are very small in area, and the majority of the historical aerial photography is not large scale, specialized methods have, through experience, been developed to do this work. The result of the work is a series of standard format film stereograms and a detailed report. The report includes several unique methods for presenting the airphoto findings.  相似文献   

Granulometric and mineral composition of the loess-paleosol formation in Moldova     

A. V. Golbert  V. A. Osiyuk Dr. 《GeoJournal》1991,24(2):175-180

The granulometric composition and sorting of loesses and interbedded soils are studied for stratigraphic subdivision and correlation of the loess-paleosol sequence in Moldova. Distinctive features of loess and paleosol horizons of different age are identified and general characteristics of the mineral composition are described that together with other lithological characteristics, including the visual ones, improve reliability of stratigraphic operations.  相似文献   

7th World Congress on water resources Rabat,Morocco, 13–18 May, 1991     

A. K. Biswas Prof. Dr. 《GeoJournal》1991,25(1):118-118

Submitted to United Nations Environment Programme Nairobi, Kenya by International Water Resources Association.  相似文献   

Density and pressure change in an occluding cyclone     

Dr. G. Ragette 《Meteorology and Atmospheric Physics》1991,46(1-2):65-75

Summary On October 20, 1974, an occluding cyclone, which did not intensify any more crossed central Europe. Considerable pressure tendencies reflecting the displacement of the storm were observed during its passage. Although horizontal density advection contributed least to density and thus pressure changes, it was still of decisive importance for both. The other larger contributors, whose net effect was usually opposed to the effect of horizontal advection, nearly cancelled each other. Thus there was a fair correlation between horizontal advection and density tendency, and the actual density and pressure changes frequently turned out smaller than if caused by advection alone.It has been shown that in the lowest 3 km usually. For the mass divergence this inequality was observed in the frontal zones where horizontal advection was considerable. In particular, warm air advection reduced the effect of horizontal velocity convergence near the warm front. Thus, vertical mass divergence became predominant and caused a density decline. Cold air advection accompanying the cold front was responsible for horizontal divergence to be overcompensated by vertical mass convergence which induced rising density.With 11 Figures  相似文献   

The effect of moist layer location on the stability of trapped gravity waves in an almost saturated atmosphere     

Dr. C. P. Jacovides  Prof. D. P. Lalas 《Meteorology and Atmospheric Physics》1991,45(1-2):65-74

Summary The stability characteristics of trapped gravity waves, generated by an isothermal bounded tanh (z) velocity profile in the presence of a saturated finite layer, are studied. The saturated layer is introduced at different levels above the inlection point and the variations of moisture content, layer thickness and distance from the origin are examined. The growthyrates and phase speeds of the unstable modes are obtained by solving numerically the equations of motion in the linear, inviscid, Boussinesq limit, via the technique of Lalas and Einaudi (1976).It is shown that the presence of the saturated layer can significantly affect the stability characteristics of the waves. inereases in moisture, layer thickness and distance of the layer from the inflection point are found to amplify the wave response because the saturated layer behaves as a top boundtry to the shear flow. The presence of such effective boundaries is found to stabilize short wavelengths and destabilize longer wavelengths. Finally, an application of the results to a rainband case produces values of the wave parameters in good agreement with the observed ones.With II Figures  相似文献   

Der Eiswinter 1990/91 im deutschen Küstengebiet zwischen Ems und Oder     

Dr. Gerhard Koslowski 《Ocean Dynamics》1991,44(1):51-56

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An overview of chromium in the marine environment     

Dr. Claus-Dieter Geisler  Dr. Diether Schmidt 《Ocean Dynamics》1991,44(4):185-196

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Local currents at a shoreface-connected ridge in the German Bight     

Holger Klein  Dr. Ekkehard Mittelstaedt 《Ocean Dynamics》1991,44(3):133-142

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