Search

The surface and subsurface karst features of the Eocene limestone plateaus along the Middle Nile Valley in Egypt were formerly believed to be epigene in origin and to have developed during post-Eocene pluvial periods. However, the morphology of the caves and their restriction to particular stratigraphic intervals suggests that they are hypogene. The geochemistry and mineralogy of the soft, thick-bedded, brown/black cave infills shows that these sediments originated from hydrothermal processes, as evidenced by their Fe, Mn, Co, Ni, and Cu concentrations. Thus, the karst features are hypogene and probably formed during the opening of the Red Sea Rift at the end of the Oligocene and early Miocene. At this time, there was abundant volcanic activity, as shown by basalt lavas ~70 km northwest of Assiut; this triggered the release of large amounts of CO2 that made the hydrothermal waters acidic and dissolved the caves. [ABSTRACT FROM AUTHOR]

The Wadi Samra–Wadi Kid district in southeastern Sinai, Egypt, has undergone extensive investigation involving remote sensing analysis, field geology studies, petrography, and geochemistry. The main aim of this study is the integration between remote sensing applications, fieldwork, and laboratory studies for accurate lithological mapping for future mineral exploration in the study region. The field relationships between these coincident rocks were studied in the study area. Landsat-8 (OLI) data that cover the investigated area were used in this paper. The different rock units in the study area were studied petrographically using a polarizing microscope, in addition to major and trace analysis using ICP-OES tools. The Operational Land Imager (OLI) images were used with several processing methods, such as false color composite (FCC), band ratio (BR), principal component analysis (PCA), and minimum noise fraction (MNF) techniques for detecting the different types of rock units in the Wadi Kid district. This district mainly consists of a volcano-sedimentary sequence as well as diorite, gabbro, granite, and albitite. Geochemically, the metasediments are classified as pelitic graywackes derived from sedimentary origin (i.e., shales). The Al2O3 and CaO contents are medium–high, while the Fe2O3 and TiO2 contents are very low. Alkaline minerals are relatively low–medium in content. All of the metasediment samples are characterized by high MgO contents and low SiO2, Fe2O3, and CaO contents. The granitic rocks appear to have alkaline and subalkaline affinity, while the subalkaline granites are high-K calc-alkaline to shoshonite series. The alkaline rocks are classified as albitite, while the calc-alkaline series samples vary from monzodiorites to granites. The outcomes of this study can be used for prospecting metallic and industrial mineral exploration in the Wadi Kid district. [ABSTRACT FROM AUTHOR]

Several outcrops of felsic melt, commonly known as oceanic plagio-granites, appear as melt pockets, irregular bosses, and dikes. Three main rock successions were exposed in the Abu Dabbab area: ophiolitic sequence, island arc assemblage, and rare metal-bearing albite granites. Plagio-granite is composed mainly of plagioclase and quartz, and chemically contains high SiO2, Al2O3, and Na2O values. The petrogenetic and geochemical studies concluded that the magmas of plagio-granites and associated felsic rocks were derived from partial melting of highly depleted mantle harzburgite and/or pre-existing oceanic crustal rocks (basalts and/or gabbros). The geochemical characteristics reveal that Abu Dabbab plagio-granites are identical to the typically low-K series of ophiolitic complexes and resemble the ocean ridge granites. Elements such as Co, Nb, Pb, and Nd in Abu Dabbab plagio-granites have high Clarke concentrations (more than 1.88). This indicates Abu Dabbab plagio-granite derived from partial melting of pre-existing oceanic crustal rocks. The average concentration values of 238 U and 232 Th are lower than those of the world's average and the average activities in granitic rocks. The scope of estimated exercises generally contrasted as their quality in rock tests relies upon their physical, synthetic, and geo-concoction properties and the appropriate condition. [ABSTRACT FROM AUTHOR]

Younger granite bodies form two arches, the western and the eastern (WA, EA), which extend from the south northwards from the Meatique, ophiolitic group-island arc rocks, to the large older granite outcrop to the north. This paper concerns the feasibility of exploration in the El-Erediya-Ria El-Garah-El-Gidami-El-Missikat Y Gr regions. Fieldwork and remote sensing, together with geochemical, petrochemical, and mineralogical studies, are used to show the controlling factors, routes, and the origins of the deposits. Remote sensing is used to delineate the different rock units. Normal and strike–slip NW, NNE faults, veins, fractured ENE shear zones, and alteration zones of magmatic-hydrothermal fluids are discussed. Granites are considered using petrochemical diagrams as resources. These rocks are categorized as syeno- and alkali feldspar granites. Geochemical binary relationships recognized the granites are highly fractionated calc-alkaline-altered Monzo-, syeno-, and alkali feldspar granites formed in the active continental margin. The observed positive Ga vs. Cu, Zn, and Ni correlations are used for epithermal-magmatic-hydrothermal polymetallic veins and mineralized greisen zones. Negative Cu vs. Mo correlation patterns show probable Mo-porphyry deposits in the deeper zones at the contact point between porphyritic perthite and perthite granitic El-Erediya mass. The Zr/Sr between 1.65 to 2.93 plus fluorites in El-Missikat and up to 5.48 plus fluorites in El-Erediya show both U-poor at El-Missikat and U-rich deposits at El-Erediya. The recorded U, Th, Cu, and Pb vertical zoning sequence of deposition differentiates U aureole and deposit zones. The estimated lateral zoning sequences of deposition of these elements define the centers of U deposits. Pathfinders for the deposit of the examined area include the positive Fe2O3 vs. Mg O and Fe2O3 vs. Ca O correlations, and also negative Rb/Sr vs. K/Na and Rb vs. Sr ones, can be applied to future prospecting for similar U-F-Au-W-Mo deposits in the Eastern Desert of Egypt. [ABSTRACT FROM AUTHOR]

Field and geochemical observations of the granitoids of the Homrit Waggat area in the central Eastern Desert of Egypt reveal two magmatic phases. The early phase of weakly deformed subduction‐related calc‐alkaline rocks includes tonalite and granodiorite. We name the later phase the Homrit Waggat Pluton (HWP); it includes undeformed syenogranite, alkali feldspar granite, and minor albitized granite. The tonalite and granodiorite have distinct negative Nb–Ta anomalies and lower alkalis, REE, Nb, Zr, and Hf than the HWP. The early magmatic pulse is a subduction‐related suite, likely generated by underplating of mantle‐derived magmas that triggered partial melting of mafic lower crust; mixing of these melts led to intermediate magma that further fractionated to tonalite and granodiorite. The HWP granites of the late magmatic pulse are transitional from a subduction‐related to an anorogenic within‐plate environment, plausibly generated by post‐collisional lithosphere delamination. Although the parent magma of the HWP was I‐type, extensive fractional crystallization produced residual liquids with A2‐type character. Albitized granites are found only along the outer margin of the HWP, and contacts with the alkali feldspar granite are gradational, suggesting fluid interactions at a late stage of crystallization. The original textures of the albitized granites are preserved, but their bulk composition was modified by the production of Na‐rich minerals and the removal of K, REE, and some trace elements by fluids. [ABSTRACT FROM AUTHOR]

The goal of impulse noise removal is to suppress the noise by preserving the integrity of edges and detail information. This paper will discuss this goal in two steps. In the first one, an overview of effective algorithms for image restoration was presented; while the second step represent a new hybrid filtering technique that suggested improving the denoising process in digital images. The filters used in this work as untrimmed decision based median filter (UDBMF) and decision based median filter (DBMF). The performance of these filters was compared based on qualitative parameters with some existing non linear filters at levels of noise up to ninety percentages. The results have shown that the suggested methodology has the potential to be applied in noise removal and a good performance is readily achievable. Also, the necessary details in image were preserved. [ABSTRACT FROM AUTHOR]

Colorless distributed combustion (CDC) has shown to provide ultra-low emissions of NO, CO, unburned hydrocarbons, and soot, with stable combustion without using any flame stabilizer. The benefits of CDC also include uniform thermal field in the entire combustion space and low combustion noise. One of the critical aspects in distributed combustion is fuel mixture preparation prior to mixture ignition. In an effort to improve fuel mixing and distribution, several schemes have been explored that includes premixed, nonpremixed, and partially premixed. In this paper, the effect of dual-location fuel injection is examined as opposed to single fuel injection into the combustor. Fuel distribution between different injection points was varied with the focus on reaction distribution and pollutants emission. The investigations were performed at different equivalence ratios (0.6-0.8), and the fuel distribution in each case was varied while maintaining constant overall thermal load. The results obtained with multi-injection of fuel using a model combustor showed lower emissions as compared to single injection of fuel using methane as the fuel under favorable fuel distribution condition. The NO emission from double injection as compared to single injection showed a reduction of 28%, 24%, and 13% at equivalence ratio of 0.6, 0.7, and 0.8, respectively. This is attributed to enhanced mixture preparation prior to the mixture ignition. OH* chemiluminescence intensity distribution within the combustor showed that under favorable fuel injection condition, the reaction zone shifted downstream, allowing for longer fuel mixing time prior to ignition. This longer mixing time resulted in better mixture preparation and lower emissions. The OH* chemiluminescence signals also revealed enhanced OH* distribution with fuel introduced through two injectors. [ABSTRACT FROM AUTHOR]

The dismembered ophiolites in Wadi Arais area of the south Eastern Desert of Egypt are one of a series of Neoproterozoic ophiolites found within the Arabian–Nubian Shield (ANS). We present new major, trace, and rare earth element analyses and mineral composition data from samples of the Wadi Arais ophiolitic rocks with the goal of constraining their geotectonic setting. The suite includes serpentinized ultramafics (mantle section) and greenschist facies metagabbros (crustal section). The major and trace element characteristics of the metagabbro unit show a tholeiitic to calc-alkaline affinity. The serpentinized ultramafics display a bastite, or less commonly mesh, texture of serpentine minerals reflecting harzburgite and dunite protoliths, and unaltered relics of olivine, orthopyroxene, clinopyroxene, and chrome spinel can be found. Bulk-rock chemistry confirms harzburgite as the main protolith. The high Mg# (91.93–93.15) and low Al2O3/SiO2ratios (0.01–0.02) of the serpentinized peridotite, together with the high Cr# (>0.6) of their Cr-spinels and the high NiO contents (0.39–0.49 wt.%) of their olivines, are consistent with residual mantle rocks that experienced high degrees of partial melt extraction. The high Cr# and low TiO2contents (0.02–0.34 wt.%) of the Cr-spinels are most consistent with modern highly refractory fore-arc peridtotites and suggest that these rocks probably developed in a supra-subduction zone environment. [ABSTRACT FROM AUTHOR]

Distributed combustion has been shown to provide significantly improved performance with near zero emissions for stationary gas turbine applications. Characteristics of distributed combustion include uniform thermal field in the entire combustion chamber (improved pattern factor), ultra-low emissions of NOx and CO, low noise, enhanced stability, and higher efficiency. Distributed combustion with swirl have been investigated to determine the beneficial aspects of such flows on clean and efficient combustion under simulated gas turbine combustion conditions with ultra-low NOx emissions. Results are presented here on the impact of employing dual injection of air and fuel in contrast to single injection. Dual and multi-injection is of great importance for combustor design scale up as to maintain flow similarities. Results showed that careful implementation of dual injection can result in emissions as low as single air/fuel injection method. With adequate fuel injection strategy, further reduction in emissions has been demonstrated. Results obtained on pollutants emission with dual injection and different fuel injection strategies at various equivalence ratios showed ultra-low emission (<5 PPM NO and <15 PPM CO) and high performance. OH* chemiluminescence revealed relative position of the flame within the combustor under various conditions for further improvements in distributed combustion conditions and to further reduce NOx emission. [ABSTRACT FROM AUTHOR]

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (~10 ppm) and CO (~21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m³-atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion. [ABSTRACT FROM AUTHOR]

A Hemoglobin (Hb) biosensor based on dual-core photonic crystal fiber is proposed and analyzed. In this paper, the effective refractive index dependency on the Hb concentration within a blood sample is utilized in obtaining the transmission spectrum variation. The results are calculated using full vectorial finite element method. Through this study, the effect of the structure geometrical parameters on the sensor performance is optimized to maximize the sensor sensitivity. The numerical results show a sensitivity of 8.013 nm/g/dL for the X-polarized mode at 3.7 cm fiber length and 7.68 nm/g/dL for the Y-polarized mode at 3.2 cm fiber length of the proposed sensor. [ABSTRACT FROM AUTHOR]