Synthesis and Characterizations of Titanium Tungstosilicate and Tungstophosphate Mesoporous Materials

The work reports a development approach for the synthesis of novel multi-components mesoporous materials of titanium tungstate (meso-TiW) titanium tungstosilicate (meso-TiWSi) and tungstophosphate (meso-TiWP) mixed oxides that have high surface area and ordered mesoporous structures at nanometer length scale. Using the solvent evaporation-induced self-assembly (EISA) new oxides of bi- and tri-component of meso-TiW, meso-TiWSi and meso-TiWP oxides with different compositions and porosity were achieved. The physicochemical properties of the mesoporous oxides were characterized by X-ray diffraction, BET surface area analyzer, scanning, and transmission electron microscopes. Subject to the oxide composition, the obtained meso-TiW, meso-TiWSi and meso-TiWP exhibits high surface area, ordered 2D hexagonal mesostructured with order channels extended over a large area. The produced meso-TiW, meso-TiWSi, and meso-TiWP adsorbents exhibit good adsorption efficiency for the removal of Pb(II), Cd(II) and Hg(II) ions from water solution due to the presence of high surface area and accessibility of surface active sites. The adsorption efficiency of these mesoporous oxide reaches up to 95% and is found to be dependent contact time and adsorbents dose. The synthesis strategy is particularly advantageous for the production of new complex (multi-component) inorganic mesoporous materials that might have an application in the field of environmental, catalysis or energy storage and production

Throughput, Spectral, and Energy Efficiency of 5G Massive MIMO Applications Using Different Linear Precoding Schemes

— A promising massive multiple input multiple output (M-MIMO) system is required to meet the growing need for highly traffic data, highly-resolution of streaming video, and intelligent communication on the fifth-generation wireless networks (5G). M-MIMO systems are essential for the optimization of the trade between energy efficiency (EE), throughput (R), and spectral _efficiency (SE) in wireless 5G networks. M-MIMO system architecture is proposed in this paper to enhance the trade-off between energy efficiency and uplink and downlink throughput at the optimum EE. Furthermore, using linear precoding techniques such as M MMSE, RZF, ZF, and MR, the EE-SE trade-off is optimized for uplink and downlink (M-MIMO) systems. The analysis of simulation results proved that throughput (R) is enhanced by increasing the number of antennas at optimum EE. After that, the proposed trading scheme is optimized and improved using M_MMSE compared to RZF, ZF. Finally, the results prove that M_MMSE gives the optimum trade-off between EE and R at the proved optimum ratio between the number of active antennas and the number of active users UE

Prevalence of Nocturnal Enuresis among Schoolchildren in Sana’a City, Yemen

Objective: To estimate the prevalence, frequency and time of nocturnal enuresis (NE) among primary schoolchildren in Sana’a city, Yemen. Methods: This was a cross-sectional study was conducted among 2689 schoolchildren in the primary schools of four randomly selected districts in Sana’a city in the period from September 2012 to December 2013. Data about sociodemographic characteristics, frequency, time, psycho-social effects and the factors possibly associated with NE among children were collected using a pre-designed questionnaire and analyzed using appropriate statistical tests. Results: The overall prevalence of NE was 11.2%, which was significantly higher among males than females (13.0% vs. 10.0%, respectively; P = 0.044) and decreased significantly with increasing age (P <0.001). More than half of children (55.3%) in Sana’a city had the habits of drinking excess fluids and tea at night and/or deep sleeping. Of physical and health disorders, difficulty in breathing and urinary tract infections were the two most frequent conditions among children with NE, being observed among 29.6% and 23.9% of cases, respectively. However, urogenital anomalies and mental retardation were the least frequent conditions in children with NE, being observed among 5.8% and 1.3% of cases, respectively. On the other hand, marital problems (24.8%) and arrival of a new baby (17.9%) were the most frequently observed social conditions among children with NE, while death in the family (8.5%) and parental separation (6.0%) were the least frequently observed conditions. Conclusions: NE is prevalent among 11.2% of schoolchildren in Sana’a city with a significantly higher, though slight, rate among males. This rate is lower than the rates reported from Aden and Mukalla cities in the country and from Saudi Arabia and Turkey. However, it is higher than those reported from Iran and Malaysia. About a third of children experience nightly NE, whereas the lowest proportion of children experience NE twice a month. The habits of drinking excess fluid and tea at night and/or deep sleeping, the disorders of difficulty in breathing and urinary tract infections and the social conditions of marital problems and arrival of a new baby are the most frequent observations among children with NE in Sana’a city

Photoelectrochemical performance of strontium titanium oxynitride photo-activated with cobalt phosphate nanoparticles for oxidation of alkaline water

Photoelectrochemical (PEC) solar water splitting is favourable for transforming solar energy into sustainable hydrogen fuel using semiconductor electrodes. Perovskite-type oxynitrides are attractive photocatalysts for this application due to their visible light absorption features and stability. Herein, strontium titanium oxynitride (STON) containing anion vacancies of SrTi(O,N)3−δ was prepared via solid phase synthesis and assembled as a photoelectrode by electrophoretic deposition, and their morphological and optical properties and PEC performance for alkaline water oxidation are investigated. Further, cobalt-phosphate (CoPi)-based co-catalyst was photo-deposited over the surface of the STON electrode to boost the PEC efficiency. A photocurrent density of ~138 μA/cm at 1.25 V versus RHE was achieved for CoPi/STON electrodes in presence of a sulfite hole scavenger which is approximately a four-fold enhancement compared to the pristine electrode. The observed PEC enrichment is mainly due to the improved kinetics of oxygen evolution because of the CoPi co-catalyst and the reduced surface recombination of the photogenerated carriers. Moreover, the CoPi modification over perovskite-type oxynitrides provides a new dimension for developing efficient and highly stable photoanodes in solar-assisted water-splitting reactions

Structure and electrochemical activity of nickel aluminium fluoride nanosheets during urea electro-oxidation in an alkaline solution

An electrocatalyst of potassium nickel aluminium hexafluoride (KNiAlF6) nanosheets has been prepared using solid-phase synthesis at 900 °C. X-ray diffraction, scanning electron microscopy, and conductivity studies confirmed the formation of KNiAlF6 nanosheets having a cubic defect pyrochlore structure with an average thickness of 60–70 nm and conductivity of 1.297 × 103 S m−1. The electrochemical catalytic activity of the KNiAlF6 nanosheets was investigated for urea oxidation in alkaline solution. The results show that the KNiAlF6 nanosheets exhibit a mass activity of ∼395 mA cm−2 mg−1 at 1.65 V vs. HRE, a reaction activation energy of 4.02 kJ mol−1, Tafel slope of 22 mV dec−1 and an oxidation onset potential of ∼1.35 V vs. HRE which is a significant enhancement for urea oxidation when compared with both bulk Ni(OH)2 and nickel hydroxide-based catalysts published in the literature. Chronoamperometry and impedance analysis of the KNiAlF6 nanosheets reveal lower charge transfer resistance and long-term stability during the prolonged urea electro-oxidation process, particularly at 60 °C. After an extended urea electrolysis process, the structure and morphology of the KNiAlF6 nanosheets were significantly changed due to partial transformation to Ni(OH)2 but the electrochemical activity was sustained. The enhanced electrochemical surface area and the replacement of nickel in the lattice by aluminium make KNiAlF6 nanosheets highly active electrocatalysts for urea oxidation in alkaline solution

Electrical characteristics of metal contacts on porous silicon

I(V) and C(V) characteristics of aluminium-porous silicon (PS) contacts were measured in the temperature range of 77-300 K for a sample prepared from 8-12 Ω·cm p-type silicon. The barrier height derived from the I(V) characteristics was found to depend linearly on temperature. The ideality factor was estimated to be 11.5 for the temperature range of 77-300 K. A decrease of contact differential capacitance, measured at 1 kHz, with decreasing temperature is observed