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.
This paper investigates the joint subcarrier and power allocation problem for the downlink of a multi-carrier non-orthogonal multiple access (MC-NOMA) system. A novel three-step resource allocation ...framework is designed to deal with the sum rate maximization problem. In Step 1, we relax the problem by assuming that each of the users can use all the subcarriers simultaneously. With this assumption, we prove the convexity of the resultant power control problem and solve it via convex programming tools to get a power vector for each user. In Step 2, we allocate the subcarriers to users by a heuristic greedy manner with the obtained power vectors in Step 1. In Step 3, the proposed power control schemes used in Step 1 are applied once more to further improve the system performance with the obtained subcarrier assignment of Step 2. To solve the maximization problem with fixed subcarrier assignments in both Step 1 and Step 3, a centralized power allocation method based on projected gradient descent algorithm and two distributed power control strategies based, respectively, on pseudo-gradient algorithm and iterative waterfilling algorithm are investigated. Numerical results show that our proposed three-step resource allocation algorithm could achieve comparable sum rate performance to the existing near-optimal solution with much lower computational complexity and outperforms power controlled OMA scheme. Besides, a tradeoff between user fairness and sum rate performance can be achieved via applying different user power constraint strategies in the proposed algorithm.
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.
God is very difficult to understand with eyes. In order to know God, His nature, and His personification, use of various symbols can be helpful, which suggests the unification of two elements, namely ...the physical and spiritual ones. Acintya is the symbol or manifestation of God 's Omnipotence. It is the “unimaginable” that turns to be the “imaginable" through potraits, reliefs, or statues. All of these symbols are manifestation of the Acintya that takes the form of the dance of Shiva Nataraja, as the depiction of the Omnipotence of God, to bring in the actual symbol of the "Unthinkable " that have a meaning that people are in a situation where emotions religinya very close with God.
Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin (Western Desert, Egypt) necessitate a ...thorough oil-source correlation investigation. This objective is achieved through a meticulous analysis of well-log responses, Rock-Eval pyrolysis, and biomarker data. The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt% to 2.04 wt%, thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen. Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter. Notably, a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed. Contrarily, the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment, and thus featuring a pronounced marine influence within a more reducing setting, which is associated with Type II kerogen. Through analysis of five oil samples from different wells—SIWA L-1X, SIWA R-3X, SIWA D-1X, PTAH 5X, and PTAH 6X, it is evident that terrestrial organic matter, augmented by considerable marine input, was deposited in an oxidizing environment, and contains Type III kerogen. Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments. Noteworthy is the uniformity of identified kerogen Types II and III across all samples, known to have potential for hydrocarbon generation. The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir, suggesting potential links to Paleozoic sources or even originating from the Safa Member itself. These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin. By illuminating the processes of hydrocarbon genesis in the region, this study significantly enriches our knowledge base.
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•Analysis of well-log responses, Rock-Eval pyrolysis, and biomarker data.•Diverse levels of organic content and the presence of both Type II and III kerogen.•Dhiffah Formation comprises a blend of terrestrial and marine organic matter.•Desouky and Zeitoun exhibit mixed organic matter with Type II oil-prone kerogen.•Jurassic Safa reservoir oil comes from Paleozoic or Safa sources.
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.
The salinization of the groundwater wells in Siwa oasis, Egypt represents a critical environmental and economic issue. Developing low-cost, effective, and self-supported inorganic membranes were ...suggested as suitable desalination techniques. Zeolite/geopolymer (Z/GP) membrane was synthesized as a potential low-cost membrane for effective desalination of brackish groundwater in Siwa Oasis, Egypt. The membrane was synthesized by simple geopolymerization for natural kaolinite and diatomite at room temperature. This was followed by hydrothermal growth of zeolite at 100 °C for 24 h to produce zeolitized geopolymer as potential inorganic membrane. After that, the prepared membrane was incorporated in the pervaporation desalination system considering the effect of the membrane thickness and the temperature. The results demonstrated water flux values of 8.34 kg.m−2.h−1, 7.63 kg.m−2.h−1, and 7.05 kg.m−2.h−1 for the tested membrane at thicknesses of 1 mm, 2 mm, and 3 mm, respectively. This associated with significant salt rejection prearranges 95.8% (1 mm), 97.6% (2 mm), and 99.4% (3 mm). Moreover, the high-temperature value (90 °C) is of strong positive impact on the water flux (7.82 kg.m−2.h−1) and a slight impact on the salt rejection (99.6%). The membrane is of significant stability considering the obtained water flux (7.51 kg.m−2.h−1) and salt rejection (99.57%) after 130 h. The reusability properties of the Z/GP membrane demonstrated its suitability to be used in the desalination process for five runs. Therefore, the synthetic Z/GP membrane is a highly recommended product for simple, effective, low cost, and available desalination technique brackish groundwater in Siwa Oasis.
•Zeolite/geopolymer membrane was used in the desalination of Siwa groundwater.•It achieved 7.82 kg.m−2.h−1 water flux and 99.6% salt rejection at 90 °C.•It is stable for 140 h with 7.5 kg.m−2.h−1 water flux and 99.57% salt rejection.•The membrane was reused for five runs with significant desalination performance.•The desalinated water matches the limitations of drinking and irrigation water.
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