Energy Efficiency of Two‐Phase Mixing in a Modified Bubble Column

Energy efficiency for gas liquid mixing in a modified downflow bubble column reactor has been analyzed in this paper. Efficiencies of the different parts of the bubble column have been assessed on the basis of energy dissipation. Prediction of the energy dissipation coefficient as well as energy utilization efficiency due to gas‐liquid mixing as a function of different physical, geometric and dynamic variables of the system has been done by correlation method. The distribution of energy utilization in the different zones of the column has also been analyzed. Experiments were carried out with air‐water and air‐aqueous solutions of carboxy methyl cellulose with different concentrations.     

Adhesion studies of tyre cords with rubber. I. Synthesis and characterization of natural rubber graft copolymers

Glycidyl methacrylate and N-vinyl pyrrolidone have been grafted onto natural rubber at 32°C using the simultaneous cobalt-60 irradiation technique. The natural rubber samples were swollen in the monomers for 24 h and thereafter subjected to gamma irradiation. The homopolymers formed in the graft copolymerization reactions and unreacted monomer were removed by solvent extraction using acetone and methanol for glycidyl methacrylate and N-vinyl pyrrolidone monomer, respectively. The influence of total dose and monomer concentration on the graft parameters was investigated. The dependence of the rate of grafting on the monomer concentration was found to be 0.93 and 0.80 for glycidyl methacrylate and N-vinyl pyrrolidone, respectively. DSC and TGA studies of the polymers were undertaken. Grafted copolymers based on glycidyl methacrylate were relatively less thermally stable compared with ungrafted natural rubber.     

Kinetic Monte Carlo simulation for homogeneous nucleation of metal nanoparticles during vapor phase synthesis

We present a free‐energy driven kinetic Monte Carlo model to simulate homogeneous nucleation of metal nanoparticles (NPs) from vapor phase. The model accounts for monomer‐cluster condensations, cluster–cluster collisions, and cluster evaporations simultaneously. Specifically, we investigate the homogeneous nucleation of Al NPs starting with different initial background temperatures. Our results indicate good agreement with earlier phenomenological studies using the Gibbs# free energy formulation from Classical Nucleation Theory (CNT). Furthermore, nucleation rates for various clusters are calculated through direct cluster observations. The steady‐state nucleation rate estimated using two different approaches namely, the Yasuoka‐Matsumoto (YM) and mean first passage time (MFPT) methods indicate excellent agreement with each other. Finally, our simulation results depict the expected increase in the entropy of mixing as clusters approach the nucleation barrier, followed by its subsequent drastic loss after the critical cluster formation resulting from first‐order phase transitions. © 2017 American Institute of Chemical Engineers AIChE J, 63: 18–28, 2018     

Pinch Roller Failure Analysis and Resulting Enhancement of Rebar Mechanical Properties

Reinforcing bars, popularly termed “rebars,” are used to impart tensile strength to concrete structures. Concrete has high resistance to weathering and fire and high compressive strength but almost no tensile strength, hence rebars are used to provide the latter to concrete. Property consistency along the length of rebars is an important prerequisite. When the finished product is subjected to thermomechanical treatment (TMT), proper control of rolling and water box parameters and efficient pinch rolling are needed to achieve acceptable properties. Variation of yield strength (YS) along TMT bars from the front to back end has been observed within the same heat treatment. In the presented investigation, it was observed that pinch rolling ineffectiveness is the main reason for the poor mechanical properties at the back end. The pinch roller was unable to support the back end of the TMT bars properly to maintain the speed and tension of the bars, resulting in nonuniform cooling of the back end through the water box and subsequent mechanical property failure. Due to the substandard material of the pinch roller, it was unable to hold the back end of the bar properly. Based on analysis of the roller it was concluded that it failed due to improper microstructure, resulting in inadequate hardness and toughness for the stringent operating conditions. AISI H13 is a better material to use in such high-service-temperature conditions. Moreover, proper heat treatment is needed to achieve adequate hardness and microstructure properties. After proper heat treatment of pinch rollers, their service life was increased twofold, minimizing the YS variation along the rebars.     

Cytochrome P450 inhibitory potential of selected Indian spices — possible food drug interaction

Spices constitute an important group of food which is virtually indispensable in the culinary art. In a view, these spices feared to pose a probability to affect the disposition of conventional pharmaceuticals through inhibition of human cytochrome P450 (CYPs) enzymes. In the present study an approach has been made to evaluate the possible CYP inhibition potential with some Indian spices (Capsicum annuum, Murraya koenigii, Zingiber officinale) and their major bioactive compounds, in combination with pooled microsome; as well as commercially available recombinant human CYP3A4, CYP2D6, CYP2C9 and CYP1A2. Quantification of the bioactive compound was determined through RP-HPLC, in order to standardize the plant material. CYP–carbon monoxide (CYP–CO) complex assay result indicated that all the plants and their bioactive compounds have an interaction potential with CYPs. Fluoregenic assay results indicated that the spice extracts have higher inhibition potential comparing to their single bioactive molecule. The higher enzyme inhibition potential by the extracts may be related to the synergistic effects due to the presence of other constituents in the extract. Capsaicin and C. annuum showed the lowest IC₅₀ value and 6-gingerol and Z. officinale extract showed the highest IC₅₀ value among the entire sample tested. The entire sample showed significantly less (P < 0.001, P < 0.01) interaction potential than known inhibitors. These findings indicate that selected spices are unlikely to cause clinically relevant drug interactions involving the inhibition of major CYP isozymes.     

Sintered 434L ferritic stainless steel-Al2O3 particulate composites containing phosphorus

Sintering of 434£ ferritic stainless steel powder compacts containing 0-8 volume %

cx-AI20 a (1 J.1m size) and 0-4 weight % phosphorus in the form of either FesP or Fe2P was carried out in the temperature range 1150°C-1300°C, and the resultant densification parameters, ultimate compressive strengths and hardnesses were measured. The results reveal that temperatures of 1150°C and 1200°C produced liquid-phase sintering when phosphorus was added in the form of FeaP. With Fe2P additions, a higher sintering temperature of 1300°C densified the composites, and an increase in the phosphorus content to 3% uniformly enhanced the sintered properties: The presence of Al20 a particles at an optimum level only improved the properties of the liquid-phase sintered composites.     

First-principles study of CaCu3B4O12 (B=Co, Rh, Ir)

Employing first-principles density functional theory based calculations we investigated the change in electronic structure of CaCu₃B₄O₁₂ compounds as one moves from 3d (Co) to 4d (Rh) to 5d (Ir) element at B site. Our study sheds light on valences of Cu and B ions as one moves from 3d to 4d to 5d based compounds. The valence of Cu in Co and Rh compound turn out to be that of less known 3+ state, while that in Ir compound turn out to be commonly known 2+ state. Our first-principles study provide microscopic understanding of these different valences of Cu, in terms of changes in the mixing of Cu x ² − y ² and B-a _1g states, driven by changes in the crystal field and spin splitting. The stronger crystal field splitting for 4d and 5d elements compared to 3d at B site drive the low-spin state at Rh and Ir site as opposed to intermediate spin in case of Co.     

Probing the influence of superhydrophobicity and mixed wettability on droplet displacement behavior

The importance of fundamental understanding of droplet dynamics and the concomitant implications of wall wettability are critical in the emergent science and technology areas including digital microfluidics and clean energy conversion. In this work, mesoscopic illustration, based on the two-phase lattice Boltzmann model, of droplet dynamics in a microchannel is presented in order to unveil the role of superhydrophobicity and mixed wettability. The impact of critical physicochemical determinants, including capillary number and droplet size, is explored in the context of droplet–wettability interactions. Temporal evolution of wetted length and wetted area for a combination of wettability scenarios is furnished in detail in order to elucidate the droplet displacement dynamics. Capillary number plays an important role with disparate droplet behavioral patterns stemming from superhydrophobic and mixed-wet wall characteristics.