Nafion based proton exchange membrane (PEM) has long been used as conventional PEM in direct methanol fuel cell (DMFC) industry. However, the high cost of Nafion membrane and other drawbacks like ...high methanol crossover hinder the advancement of this industry. This study aims to develop a low cost membrane using sulfonated poly ether ether ketone (SPEEK) polymer. Silica and silicotungstic acid (SiWA) were incorporated into the membrane matrix using solution casting method. The optimum loading of the additives was tuned and it is discovered that the SPEEK membrane containing 10 wt% of silica and 5 wt% of SiWA has the best performance due to its high proton conductivity and moderately low methanol permeability. The performance of the membrane can further be enhanced by adding (3-aminopropyl)triethoxysilane (APTES) and carbonyldiimidazole (CDI) as coupling agents. Inclusion of APTES and CDI in SPEEK could not only improve the compatibility between organic SPEEK and inorganic additives, but also improve the homogeneity and dispersity of the additives. As a result, the resultant membrane with a better dimensional stability achieves high selectivity (10.60 × 104 S.s/cm3) up to 6.5 times more than pristine SPEEK membrane and 1.3 times higher than the commercial Nafion 117 membrane.
•SPEEK/SiO2-SiWA was produced with APTES as coupling agent and CDI as promoter.•SPEEK1-AC achieved selectivity of 6.5 times higher than pristine SPEEK.•Silica-supported SiWA increased the proton conductivity of SPEEK membrane.•Improvement in homogeneity between organic SPEEK and inorganic additives.
A dual-band structure-shared antenna with large frequency ratio is proposed in this letter by integrating two substrate integrated waveguide slot antennas (SIWAs) on the branches of dipole. In the ...proposed structure, dipole is fed by coaxial connector while SIWAs are fed by two microstrip lines. To improve the stability of the dipole and the isolation among three antennas, microstrip high-pass filter is introduced. Measured results show that the proposed antenna works at 27.3−28.8 GHz with directional radiation pattern and 3.02−5.03 GHz with omnidirectional radiation pattern.
The Faghur-Siwa Basin is a large sedimentary basin in the westernmost region of the Egyptian Western Desert. The northern portion of this basin has been hydrocarbon productive for the last few ...decades, making it a subject of frequent geological and geophysical studies. The current study aims to outline the subsurface extent, geometry and structural framework of Southern Faghur-Siwa Basin. The study introduces an approach of using large data set to deduce the structural setting of a sedimentary basin and its applicability to large-scale tectonic features in similar regions worldwide. This study uses satellite-derived potential field data, data of deep wells penetrating the basement, and previous geological studies. The Gaussian filter with a cut-off wave number of 0.0225 (Radian/km) was applied to study deep and shallow anomaly sources in the area while the edge detection methods were used to outline the subsurface boundaries of these sources. The 2.5D forward modeling of magnetic and gravity delineated the basin geometry and basement depth that ranges from 1200 to 5100 m. The basement structure map created by this study showed a complex subsurface structural framework of the Southern Faghur-Siwa Basin that is dominated by N–S, NNW-SSW, NE-SW, and E-W trending faults.
•Southern Faghur-Siwa Basin has an N–S axis, 500 km length, and 100–300 km width.•Mafic intrusions underlie the northern, eastern, and western parts of the basin.•Felsic igneous rocks underlie the central and southern parts.•2.5D gravity and magnetic models reveal basement depths ranging from 1200 to 5100m.•The basin is connected to Kufra Basin from the west and Abu Tarture Basin from east.
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•There is a warming trend from the late Eocene to early Oligocene transition at Siwa Oasis.•The warming due to the high abundance of Operculina and occurrence of kaolinite and ...gypsiferous shale.•The release of mantle CO2 from volcanic episode starting in the late Eocene may cause this warming.
In the Eocene part of the Siwa Oasis, the larger foraminifera are represented by the genera Nummulites, Arxina, Operculina, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella, Gaziryina and Discocyclina in order of abundance. Operculina continues up to the early Oligocene as modern representatives in tropical regions, while the other genera became extinct. Nevertheless, the most common larger foraminiferal genus Lepidocyclina (Nephrolepidina) appears only in the lowermost Oligocene.
In spite of the Eocene–Oligocene (E/O) transition is thought to have been attended by major continental cooling at northern middle and high latitudes, we discover that at the Siwa Oasis, there is a clear warming trend from the late Eocene (extinction level of Nummulites, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella and Discocyclina) to the early Oligocene is observed due to the high abundance of Operculina and occurrence of kaolinite and gypsiferous shale deposits in both Qatrani and El Qara formations (Oligocene) at this transition. The El Qara Formation is a new rock unit proposed herein for the Oligocene (Rupelian age) in the first time.
Several episodes of volcanic activity occurred in Egypt during the Cenozoic. Mid Tertiary volcanicity was widespread and a number of successive volcanic pulses are starting in the late Eocene. The release of mantle CO2 from this very active volcanic episode may have in fact directly caused the warm Eocene–Oligocene greenhouse climate effect.
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