Identification of optimal rate-enhanced silver ELP processes for silver–ceramic composite membrane fabrication

This work targets the identification of optimal rate-enhancement technique for the electroless fabrication of silver–ceramic porous membranes. The membranes were fabricated with porous ceramic supports of 4.5?µm and porosity of 19.3% and with alternate electroless plating (ELP) processes including conventional (CEP), sonication (SOEP), and surfactant (SIEP) plating baths. The alternate processes were evaluated based on the process (conversion, plating efficiency (η), average plating rate) and membrane characteristics (percent pore densification (PPD), metal loading index (MLI)), and their combinations (η/(MLI.PPD)). Among alternate processes, SOEP has been evaluated to be the best to yield silver–ceramic membranes.     

Bulk Ultrafine-Grained Interstitial-Free Steel Processed by Equal-Channel Angular Pressing Followed by Flash Annealing

Interstitial-free steel workpieces are deformed by equal-channel angular pressing (ECAP) for equivalent strain ε_vm = 3 and ε_vm = 21 followed by flash annealing. Microstructures are analyzed by optical microscopy, scanning electron microscopy and transmission electron microscopy. Mechanical properties are evaluated by hardness testing. Yield strength of materials is calculated from hardness values. Flash annealing (at 675 °C) of ECAPed samples for ε_vm = 3 and ε_vm = 21 results in abnormal subgrain growth and abnormal grain growth, respectively. Flash annealing at 700 °C of ECAPed (at ε_vm = 3) IF steel converts abnormally grown subgrains to grains which serve as nuclei for recrystallization and that result in bimodal grain size distribution. Bimodal grain size distribution is also produced when ECAPed IF steel for ε_vm = 21 is flash annealed at 675 °C due to abnormal grain growth or secondary recrystallization. Flash annealing of IF steel samples ECAPed for low ε_vm, in the temperature range 600-675 °C, decreases the hardness continuously with increase in the annealing temperature but it increases at high ε_vm. The former is due to annihilation of defects but the later is caused by ordering of nonequilibrium boundaries. The hardening and strengthening behaviors are similar.     

Broadband sub-6 GHz flower-shaped MIMO antenna with high isolation using theory of characteristic mode analysis (TCMA) for 5G NR bands and WLAN applications

A small size neutralization line integrated flower-shaped MIMO antenna is designed and analyzed for sub-6 GHz type 5G NR frequency bands like n79 (4400–5000 MHz), n78 (3300–3800 MHz), n77 (3300–4200 MHz), and WLAN (5150–5825 MHz) applications. The novel approach of theory of characteristic mode analysis (TCMA) is introduced to provide physical insight of the designed structure and its characteristics behavior. Due to the suggested modifications in the geometry, the isolation among the patches is greatly increased. The overall miniaturized dimension of the MIMO antenna is 25 × 40 mm². The edge-edge spacing among the elements is 0.0233λ. The prototype antenna is fabricated and measured that shows good agreement compared with simulated results. The designed MIMO antenna without the presence of decoupling structure offers an isolation of 28 dB, gain of 3.6 dBi, and radiation efficiency of 69.7% at the resonant frequency. The proposed MIMO antenna covers a broad range of frequency band from 3.296 to 5.962 GHz with −10 dB impedance bandwidth of 2666 MHz and maintains a good isolation of greater than 50 dB for the entire operating band. The tested radiation efficiency and gain are 85.3% and 6.22 dBi at 3.5 GHz. Moreover, the diversity parameters of the neutralization line integrated MIMO antenna, that is, channel capacity loss (CCL) isolation, mean effective gain (MEG), total active reflection coefficient (TARC) diversity gain (DG), and envelope correlation coefficient (ECC), are analyzed and discussed in this article.     

Sequence determination of vinyl acetate–methyl acrylate copolymers by NMR spectroscopy

Vinyl acetate/methyl acrylate (V/M) copolymers were prepared by free-radical solution polymerization in benzene. Copolymer compositions were obtained from ¹H-NMR spectroscopy. Reactivity ratios for the copolymerization of V with M were calculated using the Kelen-Tudos (KT) and the nonlinear error in variables (EVM) methods. The reactivity ratios obtained from the KT and EV methods are r_V = 0.04 ± 0.03 and r_M = 7.28 ± 2.88 and r_v = 0.04 ± 0.01 and r_M = 7.28 ± 0.37, respectively. The microstructure was obtained in terms of the distribution of V- and M-centered triad sequences from ¹³C{¹H}-NMR spectra of copolymers. Homonuclear ¹H-2D-COSY and 2D-NOESY NMR were used to determine the most probable conformer for the V/M copolymer. The copolymerization behavior of the V/M copolymers as a function of conversion is also reported. © 1994 John Wiley & Sons, Inc.     

Transesterification of karanja (Pongamia pinnata) oil by solid basic catalysts

The transesterification of karanja oil with methanol was carried out using solid basic catalysts. Alkali metal‐impregnated calcium oxide catalysts, due to their strong basicity, catalyze the transesterification of triacylglycerols. The alkali metal (Li, Na, K)‐doped calcium oxide catalysts were prepared and used for the transesterification of karanja oil containing 0.48–5.75% of free fatty acids (FFA). The reaction conditions, such as catalyst concentration, reaction temperature and molar ratio of methanol/oil, were optimized with the solid basic Li/CaO catalyst. This catalyst, at a concentration of 2 wt‐%, resulted in 94.9 wt‐% of methyl esters in 8 h at a reaction temperature of 65 °C and a 12 : 1 molar ratio of methanol to oil, during methanolysis of karanja oil having 1.45% FFA. The yield of methyl esters decreased from 94.9 to 90.3 wt‐% when the FFA content of karanja oil was increased from 0.48 to 5.75%. The performance of this catalyst was not significantly affected in the presence of a high FFA content up to 5.75%. The catalytic activities of Na/CaO and K/CaO were also studied at the optimized reaction conditions. In these two cases, the reaction initially proceeds slowly, however, leading to similar yields as in the case of Li/CaO after 8 h of reaction time. The purified karanja methyl esters have an acid value of 0.36 mg KOH/g and an ester content of 98.6 wt‐%, which satisfy the American as well as the European specifications for biodiesel in terms of acid value and ester content.     

Hydrogen Plasma Processing of Iron Ore

Iron is currently produced by carbothermic reduction of oxide ores. This is a multiple-stage process that requires large-scale equipment and high capital investment, and produces large amounts of CO₂. An alternative to carbothermic reduction is reduction using a hydrogen plasma, which comprises vibrationally excited molecular, atomic, and ionic states of hydrogen, all of which can reduce iron oxides, even at low temperatures. Besides the thermodynamic and kinetic advantages of a hydrogen plasma, the byproduct of the reaction is water, which does not pose any environmental problems. A review of the theory and practice of iron ore reduction using a hydrogen plasma is presented. The thermodynamic and kinetic aspects are considered, with molecular, atomic and ionic hydrogen considered separately. The importance of vibrationally excited hydrogen molecules in overcoming the activation energy barriers, and in transferring energy to the iron oxide, is emphasized. Both thermal and nonthermal plasmas are considered. The thermophysical properties of hydrogen and argon–hydrogen plasmas are discussed, and their influence on the constriction and flow in the of arc plasmas is considered. The published R&D on hydrogen plasma reduction of iron oxide is reviewed, with both the reduction of molten iron ore and in-flight reduction of iron ore particles being considered. Finally, the technical and economic feasibility of the process are discussed. It is shown that hydrogen plasma processing requires less energy than carbothermic reduction, mainly because pelletization, sintering, and cokemaking are not required. Moreover, the formation of the greenhouse gas CO₂ as a byproduct is avoided. In-flight reduction has the potential for a throughput at least equivalent to the blast furnace process. It is concluded that hydrogen plasma reduction of iron ore is a potentially attractive alternative to standard methods.     

An overview of selected topics in smart grids

Smart technologies when used in the traditional grid infrastructure will provide a different environment and working conditions in the grid by bringing the required smartness into the grid, called the smart grid. The smart grid can play a major role in the upcoming days to come because there is a necessity to integrate coordinated renewable energy resources into the grid and to operate the grids at a higher efficiency considering many aspects including reliability of the supply. Apart from this, there is a necessity to manage the demand supply gap in the smart grid by optimally scheduling the generators or by effectively scheduling the demand side resources instead of going for the traditional methods like partial or full load shedding. This paper presents an overview on the present state-of-the-art of smart grid technologies and broadly classifies the papers referred into two major areas, papers based on improvement of operational efficiency in smart grids and papers based on smartness in maintaining the demand supply gap. Some of the papers projected in this work also give a brief overview of the necessity of the smart grid.     

Gene-expression programming for the assessment of surface mean pressure coefficient on building surfaces

Building Simulation - Wind surface mean pressure coefficient (C?p) is an essential parameter for the assessment of wind induced forces that is a must input to all structural designs. An...