One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.     

A novel low voltage very low power CMOS class AB current output stage with ultra high output current drive capability

In this paper a novel low voltage (LV) very low power (VLP) class AB current output stage (COS) with extremely high linearity and high output impedance is presented. A novel current splitting method is used to minimize the transistors gate–source voltages providing LV operation and ultra high current drive capability. High linearity and very high output impedance are achieved employing a novel resistor based current mirror avoiding conventional cascode structures to be used. The operation of the proposed COS has been verified through HSPICE simulations based on TSMC 0.18 μm CMOS technology parameters. Under supply voltage of ±0.7 V and bias current of 5 μA, it can deliver output currents as high as 14 mA with THD better than ?53 dB and extremely high output impedance of 320 MΩ while consuming only 29 μW. This makes the proposed COS to have ultra large current drive ratio (I_outmax/I_bias or the ratio of peak output current to the bias current of output branch transistors) of 2800. By increasing supply voltage to ±0.9 V, it can deliver extremely large output current of ±24 mA corresponding to 3200 current drive ratio while consuming only 42.9 μW and exhibiting high output impedance of 350 MΩ. Interestingly, the proposed COS is the first yet reported one with such extremely high output current and a THD even less than ?45 dB. Such ultra high current drive capability, high linearity and high output impedance make the proposed COS an outstanding choice for LV, VLP and high drive current mode circuits. The superiority of the proposed COS gets more significance by showing in this work that conventional COS can deliver only ±3.29 mA in equal condition. The proposed COS also exhibits high positive and negative power supply rejection ratio (PSRR+/PSRR?) of 125 dB and 130 dB, respectively. That makes it very suitable for LV, VLP mixed mode applications. The Monte Carlo simulation results are provided, which prove the outstanding robust performance of the proposed block versus process tolerances. Favorably the proposed COS resolves the major limitation of current output stages that so far has prevented designing high drive current mode circuits under low supply voltages. In brief, the deliberate combination of so many effective novel methods presents a wonderful phenomenal COS block to the world of science and engineering.     

Green synthesis and characterization of RGO/Cu nanocomposites as photocatalytic degradation of organic pollutants in waste-water

Recently, nanocomposite photocatalysts based on semiconductors have attracted much attention due to their suitable bandgap. Combination of tow of several semiconductors can slow down the electron-hole recombination. In this regard, we have depicted an eco-friendly and green fabrication technique to synthesize RGO/Cu nanocomposite by the reduction of graphene oxide and Cu²⁺ ion utilizing spearmint extract as a reductant and capping agent. The sample was identified by FTIR, XRD, FESEM, EDS, HRTEM, and CV. The results of photocatalytic performance revealed that RGO/Cu is an efficient catalyst for degrading organic pollutants. This compound can eliminate Rhodamine B (RhB) and Methylene blue (MB) 91.0% and 72.0%, respectively.     

Studying the electronic and phononic structure of penta-graphane

In this paper, we theoretically consider a two dimensional nanomaterial which is a form of hydrogenated penta-graphene; we call it penta-graphane. This structure is obtained by adding hydrogen atoms to the sp² bonded carbon atoms of penta-graphene. We investigate the thermodynamic and mechanical stability of penta-graphane. We also study the electronic and phononic structure of penta-graphane. Firstly, we use density functional theory with the revised Perdew–Burke–Ernzerhof approximation to compute the band structure. Then one–shot GW (G₀W₀) approach for estimating accurate band gap is applied. The indirect band gap of penta-graphane is 5.78 eV, which is close to the band gap of diamond. Therefore, this new structure is a good electrical insulator. We also investigate the structural stability of penta-graphane by computing the phonon structure. Finally, we calculate its specific heat capacity from the phonon density of states. Penta-graphane has a high specific heat capacity, and can potentially be used for storing and transferring energy.     

High temperature water gas shift reaction over Fe-Cr-Cu nanocatalyst fabricated by a novel method

Fe-Cr-Cu nanocatalyst was synthesized through an inorganic-precursor thermolysis approach and exploited for high temperature water gas shift reaction. The results demonstrated that the method used for the nanocatalyst fabrication led to smaller crystallite size (32.9 nm) and higher BET surface area (127.3 m²/g) compared to those of a reference sample (65.5 nm, 78.6 m²/g) prepared by co-precipitation conventional method. Furthermore, the obtained data for catalytic activity showed that the catalyst prepared via inorganic precursor has better activity than the reference sample in all studied temperatures (350-500 °C) and also exhibited higher catalytic activity than a commercial Fe-Cr-Cu catalyst in higher temperatures (more than 450 °C).     

Correlation of polymerization conditions with drag reduction efficiency of poly(1-hexene) in oil pipelines

High molecular weight with long linear side branches are frequently used in oil pipelines as one of the main classes of drag reducer agents (DRAs). We studied the effects of polymerization conditions, including reaction temperature, monomer concentration and cocatalyst concentration ratio (Al/Ti), on the polymerization yield and molecular weight of the resultant poly(1-hexene) made by Ziegler–Natta catalyst and their consequent effects on the drag reduction efficiency in a loop test. The experimental results verified that the catalyst activity increased from 115 to 220 kgPH/molTi.atm, while the molecular weight of poly(1-hexene) dropped from 2100 to 1030 kDa, as the reaction temperature was increased from 0 to 50 °C. The loop test results also revealed that the highest pressure drop was achieved using the polymer synthesized at 0 °C and by subsequent increase in reaction temperature the pressure drop decreased. Furthermore, the catalyst activity increased from 143 to 262 kgPH/molTi.atm by increasing Al/Ti ratio, while the molecular weight increased up to a maximum level of 1500 kDa at Al/Ti = 143 and decreased at higher cocatalyst contents. Similarly, the results showed the maximum pressure drop of 20 % at Al/Ti = 143. Finally, by increasing monomer concentration, the catalyst activity and polymer molecular weight increased from 75 to 262 kgPH/molTi.atm for the former, and from 700 to 1800 kDa for the latter which resulted in maximum pressure drop by 25 %. Moreover, the pressure drop for each utilized poly(1-hexene) was increased proportionately with DRA’s concentration, and interestingly enough, DRAs were further effective at more turbulent flows with higher Reynolds numbers.     

Fabrication and characterization of microencapsulated PA with SiO<Subscript>2</Subscript> shell through sol–gel synthesis via sodium silicate precursor

In the present study, the microencapsulated phase change material with palmitic acid as core and inorganic SiO₂ shell was successfully fabricated by a sol–gel method in alkaline medium via sodium silicate precursor. The chemical compositions, crystalloid phase, microstructure and morphology of PA@SiO₂ microcapsule were studied by Fourier transform infrared spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis were used to determine the thermal properties and thermal stability of microcapsules, respectively. According to the XRD and FT-IR results, all the characteristic peaks of PA and SiO₂ were observed and there is no chemical reaction between them. Scanning electron microscopy images indicated that the microcapsule synthesized in pH 11 had a perfect spherical shape with smooth surfaces compared with other samples, and transmission electron microscopy images confirm that the PA have been well encapsulated by SiO₂. Differential scanning calorimetry analysis showed that the microcapsules indicated similar phase change behaviors as those of pristine PA, which melt at 67.2?°C with a latent heat of 111.2 J/g and freezing at 56.5?°C with a latent heat of 103.2 J/g. TGA analysis indicated that the thermal stability of the PA was also improved due to the protection of SiO₂ shell toward the encapsulated PA.     

CEDAR: Modeling impact of component error derating and read frequency on system-level vulnerability in high-performance processors

Reliability of the current microprocessor technology is seriously challenged by radiation-induced soft errors. Accurate Vulnerability Factor (VF) modeling of system components is crucial in designing cost-effective protection schemes in high-performance processors. Although Statistical Fault Injection (SFI) techniques can be used to provide relatively accurate VF estimations, they are often very time-consuming. Unlike SFI techniques, recently proposed analytical models can be used to compute VF in a timely fashion. However, VFs computed by such models are inaccurate as the system-level impact of soft errors is overlooked.     

Physical and Morphological Properties of Combined Treated Wood Polymer Composites by Maleic Anhydride and Methyl Methacrylate

Wood polymer composites were prepared by consecutive impregnation with maleic anhydride (MAN) and methyl methacrylate (MMA). Samples impregnated with MAN alone, were heated at 120°C and 150°C for 4 and 8 h. Based on the Fourier transform infrared (FT-IR) analysis and soaking-drying test results, treatment with MAN at 150°C for 4 h resulted in formation of stable crosslinks. In the second stage, MMA was used for in situ polymerization within MAN-treated wood. Field emission scanning electron microscopy observation and FT-IR analysis indicated that MMA copolymerized with MAN, and the resultant polymer filled up the lumen and is also grafted on to the cell wall. Improvement of water repellency and dimensional stability were observed in the treated samples, particularly in combined treated samples. The MAN/MMA treatment improved interaction between polymer and wood.