The microwave opacity of Saturn's rings at wavelengths of 3.6 and 13 cm from Voyager 1 radio occultation     

G.Leonard Tyler  Essam A. Marouf  Richard A. Simpson  Howard A. Zebker  Von R. Eshleman 《Icarus》1983,54(2):160-188

Radio occultation observations of Saturn's rings with Voyager 1 provided independent measurements of complex (amplitude and phase) microwave extinction and near-forward scattering cross section of the rings at wavelengths (λ) of 3.6 and 13 cm. The ring opening was 5.9°. The normal microwave opacities, τ[3.6] and τ[13], provide a measure of the total cross-sectional area of particles larger than about 1 and 4 cm radius, respectively. Ring C exhibits gently undulating (～ 1000 km) structure of normal opacity τ[3.6] ? 0.25 except for several narrow imbedded ringlets of less than about 100 km width and τ[3.6] ～ 0.5 to 1.0. The normalized differential opacity Δτ/τ[3.6], where Δτ = τ[3.6] ? τ[13], is about 0.3 over most of ring C, indicating a substantial fraction of centimeter-size particles. Some narrow imbedded ringlets show marked increases in Δτ/τ[3.6] near their edges, implying an enhancement in the relative population of centimeter-size and smaller particles at those locations. In the Cassini division, several sharply defined gaps separate regions of opacity τ ～ 0.08 and τ ～ 0.25; the opacity in the Cassini Division appears to be nearly independent of λ. The boundary features at the outer edges of ring C and the Cassini Division are remarkably similar in width and opacity profile, suggesting a similar dynamical control. Ring A appears to be nearly homogeneous over much of its width with 0.6 < τ[3.6] < 0.8 but with considerable thickening, to τ[3.6] ～ 1.0, near its inner boundary with the Cassini division. Normalized differential opacity decreases from ～0.3 at the inner and outer edges of ring A to Δτ/τ[3.6] ～ 0 at a point about one-third of the distance from the inner edge to the outer. The inner one-fourth of ring B has τ[3.6] ～ 1.0, except very near the boundary with ring C, where it is greater. The outer three-fourths of ring B has $\text{τ[3.6] ? 1.2}$. The differential opacity for the inner one-fourth of ring B is Δτ/τ[3.6] ～ 0.15. There are no gaps in ring B exceeding about 2 km in width. Ring F was observed at 3.6 cm as a single ringlet of radial width $\text{? 2}\text{km}$, but was not detected in 13 cm data.  相似文献   

Models for Fitting Gravimetric Geoids and GPS Results     

EssamGhanem  LIJiancheng 《地球空间信息科学学报》2002,5(1):28-30

The aim of this investigation is to study how to use a gravimetric(quasi) geoid for levelling by GPS data in an optimal way.The advent of precise geodetic GPS has made the use of a technique possible,which might be called GPS- gravimetric geoid determination.In this approach,GPS heights above the reference ellipsoid are determined for points whose levelled (orthometric) height H is above sea level people have already surveyed;for these points,we thus have the values of the geoid undulation N.These values are then used to constrain the geoid undulations N‘ obtained from the gravimetric solution.  相似文献   

Mineralogical and geochemical studies on Egyptian (U.A.R.) black sands     

Dr. Essam E. El-Hinnawi 《Contributions to Mineralogy and Petrology》1964,9(6):519-532

The economic mineral constituents of the black sand deposits occurring at the outpourings of the Nile Delta, Egypt, were studied from the mineralogical and geochemical point of view. These include magnetite, ilmenite, zircon, monazite, rutile und garnet. Microscopical, X-ray, chemical und spectrographic analyses are reported and discussed for each mineral.

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Zusammenfassung Die wirtschaftlich wichtigen Mineralkomponenten der Schwarzsand-Ablagerungen, die an den Mündungen des Nildeltas in Ägypten vorkommen, wurden in mineralogischer und geochemischer Hinsicht untersucht. Sie enthalten Magnetit, Ilmenit, Zirkon, Monazit, Rutil und Granat. Mikroskopische, röntgenographische, chemische und spektrographische Analysen werden für jedes Mineral angeführt und diskutiert.

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With 9 Figures in the Text  相似文献   

Economic evaluation of using marine dredged material for erosion control along the northeast coast of the Nile Delta,Egypt     

Omran Frihy  Wahid Moufaddal  Essam Deabes  Essam El Din Helmy 《Arabian Journal of Geosciences》2016,9(14):637

The present study is the first attempt in Egypt to assess feasibility of using of dredging material from Damietta Harbor in the northwestern Nile Delta for erosion control. The study also provides an economic evaluation for the shoreline management alternatives selected to mitigate for the effects of coastal erosion at two pilot eroding areas (namely, A and B) located near the Damietta Harbor. Results of compatibility analysis reveal that the dredging material is fairly compatible with the native sand of the nearby eroding beaches. In addition to soft nourishment by dredged sand, other types of coastal engineering measures which are often used in erosion management area were also evaluated as alternatives for erosion control and mitigation solution. Economic feasibility assessment by means of cost-benefit analysis of direct and indirect items has been carried out to facilitate comparison between these alternatives. Analysis of alternatives has been also supported by other criteria to select the cost-effective and environmentally acceptable option to protect the eroding pilot areas. These criteria include the high total cost paid for maintenance of the Damietta Harbor channel with no use, anticipated impacts on the littoral system, sustainability, future plans for protection of the existing coastlines, and lessons learned from previous shore protection works in the Nile Delta. The final selection of the best viable alternative indicates that the procedure of beach nourishment is the most appropriate form for protection area A, while a combination of groins and sand nourishment is more relevant for area B. In any case, material dredged from the navigation approach of the Damietta Harbor should be utilized as a borrow material in the nourishment schemes and excluding use of the terrestrial sources.  相似文献   

Study the feasibility of using PPP for establishing CORS network     

Mostafa Rabah  Zaki Zedan  Essam Ghanem  Ahmed Awad  Ahmed Sherif 《Arabian Journal of Geosciences》2016,9(13):613

Nowadays many continuously operating reference stations (CORS) network were established in Middle East to improve the surveying tasks. Establishing such geodetic control networks can be a costly business where multiple stations should be occupied simultaneously and post-processed with scientific software. Recently, precise point positioning (PPP) provides precise positioning values that may be an alternative to precise relative processing. The current research aims to investigate that PPP has a potential as a reliable absolute positioning technique operational simplicity as well as to investigate the capability of PPP approach to be a low cost alternative to the conventional positioning methods used in position determination of core networks stations. In comparison with common relative GPS techniques, the costs are reduced; because no base stations and no simultaneous observations are necessary, no need for control network maintenance which could be the most defective factors that Egypt HARN network suffered from. To see the feasibility study of using PPP for precise determination of the CORS, 14 days of GNSS data for the 14 Kuwait integrated with 27 IGS stations were processed by Bernese software to calculate the precise coordinates of Kuwaiti CORS network in the latest terrestrial geodetic frame. Three days of these data were processed by Trimble business center software and using PPP approach to calculate the precise coordinates of Kuwait network. In the current research, a comparable investigation was carried out between the coordinates obtained from Bernese software, Trimble business center, and PPP approach. The comparison proved high level of agreement between the coordinates which confirm that PPP approach can be applied for establishment of CORS network.  相似文献   

Remarks on “biaxial” calcite     

Essam E. El-Hinnawi 《Contributions to Mineralogy and Petrology》1973,38(4):339-341

Biaxial calcite grains occur in several Egyptian carbonate rocks. The degree of biaxiality is nearly consistent; the optic axial angle being in the range of 8–10°. The reasons of this “biaxiality” are discussed and it is urged that this phenomenon should be considered both in research and teaching.  相似文献   

Geochemistry of ground waters from some localities West of the Nile Delta     

Prof. Dr. Essam E. El-Hinnawi  Mr. S. M. Atwa 《International Journal of Earth Sciences》1973,62(1):225-245

The geochemistry of ground waters from Tahrir Province and Wadi El-Natrun, both West of the Nile Delta, has been studied in detail. The distribution of cations and anions in the water shows that the concentration of calcium and magnesium is lower in Wadi El-Natrun than in Tahrir, while sodium, carbonate and bicarbonate and chloride ions are higher. The concentration of potassium and sulphate ions is identical.The regional variations in the chemistry of the ground waters have been studied in detail using iso-concentration maps of both cations and anions. The trends of variation from the Nile Delta towards Wadi El-Natrun are characterized by an increase in the salinity and hence an increase in the concentration of most anions and cations.Using Collins bar graphs, the relationships between cations and anions and the salt assemblages encountered in the waters are outlined.The ground waters of Tahrir and Wadi El-Natrun are classified as recycled, good potable to fresh waters. They belong mainly to the sodium bicarbonate and Ca-Mg bicarbonate classes. The seasonal changes in the composition of the water have been studied in detail over a period of about one year.

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Zusammenfassung Diese Arbeit beschäftigt sich mit der Geochemie der Grundwässer der Tahrir-Provinz und des Gebietes des Wadi El-Natrun, westlich vom Nildelta.Die Verteilung der Kationen und Anionen in diesen Wässern zeigt, daß der Gehalt an Kalzium und Magnesium niedriger, dagegen der Gehalt an Natrium-, Karbonat- und Chloridionen höher im Gebiet des Wadi El-Natrun, als in der Tahrir-Provinz ist. Kalium- und Sulfat-Gehalte sind identisch.Die regionalen Unterschiede im Chemismus der Grundwässer wurde mit Hilfe der Iso-Konzentrationskarte von Kationen und Anionen untersucht. Vom Nildelta bis Wadi El-Natrun wird eine zunehmende Tendenz der Salinität bzw. der meisten Kationen und Anionen festgestellt.Es wird der Zusammenhang zwischen Anionen und Kationen und die Salzzusammensetzung der Wässer beschrieben. Die Grundwässer der Tahrir-Provinz und des Wadi El-Natrun sind genetisch als Kreislaufwässer zu betrachten. Sie besitzen überwiegend eine Natrium-Bikarbonat- und Kalzium-Magnesium-Bikarbonat-Vormacht. Im Laufe eines Jahres wurden die periodisch auftretenden Unterschiede im Chemismus der Wässer von Tahrir und Wadi El-Natrun gründlich untersucht.

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Résumé Ce travail a pour but l'étude de la géochimie des eaux souterraines dans la province de Tahrir et dans la région de Wadi El-Natrum (Egypte), à l'W du delta du Nil. La répartition des cations et des anions dans ces eaux montre que la teneur en Ca et Mg est plus faible, et celle en Na, carbonates et chloride, plus élevée, dans la région de Wadi El-Natrum que dans la province de Tahrir. Les teneurs en K et en sulfates sont identiques.Les différences régionales dans la composition chimique des eaux souterraines ont été évaluées à l'aide de cartes d'isoconcentrations de cations et d'anions.Du delta du Nil jusque Wadi El-Natrum, la salinité tend à augmenter. L'auteur exprime le caractère unitaire existant entre les anions et cations et la composition des sels. Les eaux de Tahrir et de Wadi El-Natrun sont des eaux météoriques. Elles possèdent de façon prédominante du bicarbonate de Na et du bicarbonate de Ca-Mg. Les différences de chimisme périodiques qu'elles subissent au cours d'une année ont été étudiées.

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Tahrir Wadi El-Natrun . , Wadi El-Natrun , , , Tahrir. . - . Wadi El-Natrun. . . Tahrir Wadi El-Natrun . . . - . .

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Petrographical and geochemical studies on egyptian (U.A.R.) Basalts     

Essam E. El-Hinnawi 《Bulletin of Volcanology》1965,28(1):283-292

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Seismicity and major geologic structures of Tiran and Sanafir islands and their surroundings in the Red Sea     

Hamdy A. Aboulela  Essam Aboud  Rashad A. Bantan 《Environmental Earth Sciences》2017,76(23):793

Tiran and Sanafir islands and their surrounding areas are very important due to their location within the Red Sea, which is in a triple junction among the African and Arabian plates and the Sinai Peninsula microplate. Consequently, this area should be studied from a geological point of view, particularly because there is a plan to construct King Salman’s bridge connecting Egypt and Saudi Arabia. Freely available potential field data, such as magnetic and gravity data, were integrated with seismological data from nearby seismic stations to understand the regional structure and seismic activity in the area. Potential field data were analysed using edge detection techniques (Tilt DeRivative and horizontal gradient) for qualitative interpretation and 2D inversion modelling for quantitative interpretation. Seismological data were analysed geostatistically to identify many epicentre locations and estimate the focal depths. The results of the potential field data analysis indicate that Tiran and Sanafir islands are located along a subsurface geological edge trending NW, parallel to the Red Sea. A similarity in potential field anomalies between both islands and the southern Sinai Peninsula indicates that these islands were separated from the Sinai Peninsula during the formation of the Gulf of Aqaba via Dead Sea Transform fault. The analysis of the seismic data indicates that a specific motion characterizes each focal depth solution. The seismic events are related to main structural trends NW–SE and NE–SW.  相似文献   

Enhanced Methyl Orange Removal Using a Newly Isolated Bacterial Strain and Potassium‐Iodide‐Doped Hydroxyapatite Nanoparticles     

Mona Kilany  Essam H. Ibrahim  Ali Alshehri  Hamed A. Ghramh 《洁净——土壤、空气、水》2019,47(7)

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