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971.
Mohamed Adel Sharaf 《Astrophysics and Space Science》1985,112(1):51-68
In this paper of the series, elliptic expansions in terms of the sectorial variables
j
j
introduced recently in Paper IV (Sharaf, 1982) to regularise highly oscillating perturbations force of some orbital systems will be established analytically and computationally for the seventh and eighth categories. For each of the elliptic expansions belonging to a category, literal analytical expressions for the coefficients of its trigonometric series representation are established. Moreover, some recurrence formulae satisfied by these coefficients are also established to facilitate their computations, numerical results are included to provide test examples for constructing computational algorithms. 相似文献
972.
Mohamed Zerka Jean-Yves Cottin Michel Grégoire Jean-Pierre Lorand MHamed Megartsi Mohamed Midoun 《Comptes Rendus Geoscience》2002,334(6):387-394
Numerous ultramafic xenoliths occur within the A??n–Temouchent volcanic complex (Northwestern Oranie, Algeria). Most of them are type I mantle tectonites (lherzolites and harzburgites) and composite xenoliths (harzburgite/clinopyroxenite) are rare. Only a few samples of spinel lherzolites display relatively fertile compositions when the major part of type I xenoliths have refractory major element compositions but enriched LREE contents showing that they have been affected by mantle metasomatism. The composite xenoliths are witnesses of reactions of alkaline magmas with the upper mantle. An asthenospheric rising, in relation with the large strike slip fault affecting the North African plate margin at Trias time is proposed as a possible geodynamical setting. To cite this article: M. Zerka et al., C. R. Geoscience 334 (2002) 387–394. 相似文献
973.
In the western Ahaggar shield, the transition between the Precambrian and the Ordovician units is characterised by thick volcano-sedimentary series (‘Série pourprée’ of the Ahnet). This series, in part of Cambrian age, results from the demolition of the Panafrican belt. Similar series were known in grabens located between the West African craton and the Ahaggar, from the ‘Adrar des Iforas’, in the south, to the Ougarta belt, in the north. We describe in this study a new formation identical to the ‘Série pourprée’ of the Ahnet, but cropping out in the far Southeast of the Ahaggar (In Guezzam). This new datum improves the Panafrican belt configuration. To cite this article: H. Djellit et al., C. R. Geoscience 334 (2002) 789–794. 相似文献
974.
The Saharan Metacraton 总被引:2,自引:0,他引:2
Mohamed G. Abdelsalam Jean-Paul Ligeois Robert J. Stern 《Journal of African Earth Sciences》2002,34(3-4)
This article introduces the name “Saharan Metacraton” to refer to the pre-Neoproterozoic––but sometimes highly remobilized during Neoproterozoic time––continental crust which occupies the north-central part of Africa and extends in the Saharan Desert in Egypt, Libya, Sudan, Chad and Niger and the Savannah belt in Sudan, Kenya, Uganda, Congo, Central African Republic and Cameroon. This poorly known tract of continental crust occupies 5,000,000 km2 and extends from the Arabian-Nubian Shield in the east to the Tuareg Shield to the west and from the Congo craton in the south to the Phanerozoic cover of the northern margin of the African continent in southern Egypt and Libya. The term “metacraton” refers to a craton that has been remobilized during an orogenic event but is still recognizable dominantly through its rheological, geochronological and isotopic characteristics. Neoproterozoic remobilization of the Saharan Metacraton was in the forms of deformation, metamorphism, emplacement of igneous bodies, and probably local episodes of crust formation related to rifting and oceanic basin development. Relics of unaffected or only weakly remobilized old lithosphere are present as exemplified by the Archean to Paleoproterozoic charnockites and anorthosites of the Uweinat massif at the Sudanese/Egyptian/Libyan boarder. The article explains why the name “Saharan Metacraton” should be used, defines the boundaries of the metacraton, reviews geochronological and isotopic data as evidence for the presence of pre-Neoproterozoic continental crust, and discusses what happened to the Saharan Metacraton during the Neoproterozoic. A model combining collisional processes, lithospheric delamination, regional extension, and post-collisional dismembering by horizontal shearing is proposed. 相似文献
975.
Mohamed I. A. Ibrahim 《Cretaceous Research》2002,23(6):775
Quantitative analyses of palynomorph assemblages, particulate organic matter (kerogen), and total organic carbon (TOC) have been made on samples of the Albian–Cenomanian Kharita and Bahariya formations encountered in the Abu Gharadig-5 well, Western Desert, Egypt. Two assemblage palynozones are defined: Assemblage Zone A (Kharita Formation) of late Albian–early Cenomanian age and Assemblage Zone B (Bahariya Formation) of early–middle Cenomanian age. Palynofacies of the Kharita Formation suggest that sedimentation of these strata took place in a warm, shallow, nearshore-marine environment. The deposition of the lower Bahariya Formation took place initially in similar conditions but subsequently further offshore in somewhat deeper water of the inner shelf. The relatively high percentage of Ephedripites, Afropollis and elaterate pollen in both formations indicates an arid climate. The Kharita Formation yields kerogen types III and IV whereas the assemblages recovered from the Bahariya Formation contain types II and III. The TOC is generally between 0.42 and 0.65% in the Kharita Formation, while it ranges between 0.42 and 0.80% in samples of the Bahariya Formation. The spores and pollen grains are pale in colour; hence little source potential for hydrocarbons is indicated. 相似文献
976.
Several series of one-dimensional tests were used to study the nature of transient heat and moisture movements in a clay buffer under different imposed temperature gradients. The measured temperature and moisture profiles were used to calculate the diffusion parameters governing heat and moisture movement in the buffer material. The experimentally determined diffusion parameters are shown to be dependent on the moisture content and temperature. The diffusion parameters were calculated by using an identification technique, the root-time method, and an analytical technique. 相似文献
977.
Mohamed Adel Sharaf 《Astrophysics and Space Science》1987,129(1):19-38
In this paper of the series, the third step of the author's regularization approach will be started by establishing the expansions of the functionX
n
(r)
(, ,u) in terms of the sectorial variables
j
(i)
introduced in Paper IV (Sharaf, 1982) to regularize the highly-oscillating perturbation force of some orbital systems. The literal analytical expressions for the Fourier expansion of the function will be explored in terms of
j
(i)
for anyn positive integer,r any real number whatever the types and the number of sectors forming the divisions situation of the elliptic orbits may be. The basic computational materials of the theory will also be given and for which the method of solution, the recurrence formulae, and the general computational sequence for the coefficients are considered. 相似文献
978.
Mohamed Adel Sharaf 《Earth, Moon, and Planets》1988,42(2):115-131
In this paper of the series, the literal analytical expressions for the Fourier expansion of the Earth's spherical harmonic potential will be explored in terms of the sectorial variables
j
(i)
introduced in Paper IV (Sharaf, 1982) to regularize the highly-oscillating perturbation force of some orbital systems.Now at the Department of Astronomy, King Abdulaziz University Jeddah, Saudi Arabia. 相似文献
979.
BeacherosionalongthecoastlineofAlexandria,Egypt¥OmranE.Frihy,SamirM.Nasr,KhalidDewidarandMohamedElRaey(ReceivedJanuary28,1993... 相似文献
980.
Caterina Casagranda Mohamed Sadok Dridi Charles Franois Boudouresque 《Estuarine, Coastal and Shelf Science》2006,66(3-4):437-446
Abundance, population structure and production of the macro-invertebrates belonging to the functional feeding group of the shredders were studied in the Ichkeul wetland, northern Tunisia, from July 1993 to April 1994. Mean above-ground macrophyte biomass was at a maximum in September followed by a complete breakdown of the Potamogeton pectinatus L. meadow from October onward due to high salinity following an exceptionally dry winter. Only the meadow of Ruppia cirrhosa (Petagna) Grande at Tinja remained in place. Abundance of Gammarus aequicauda (Martynov 1931), Idotea chelipes (Pallas 1766) and Sphaeroma hookeri Leach 1814 was significantly related to the R. cirrhosa biomass. Gammarus aequicauda presented two recruitment periods in spring and autumn, and S. hookeri a third one in winter. The population of I. chelipes was renewed during winter by continued reproduction without any spring generation. Recruitment of all three species was not very successful during the study period. Life span of all three species was between 12 and 15 months. Despite their relatively low biomass and production rate, the shredders have a key function in processing macrophyte matter to different trophic levels through fragmentation and accelerating the decomposition of macrophyte biomass accumulated at the end of the growth season in the Ichkeul lagoon. 相似文献