Economic assessment of carbon capture by minichannel absorbers

In this work, a physio‐economic model supported by lab‐scale experiments assessing the economic viability of minichannel based carbon capture units is presented. The net present value of (capital and operating) costs (NPVC) ensued throughout the plant life is selected as the benchmarking parameter. An optimization problem is formulated and solved with the objective of minimizing the NPVC of the unit subject to constraints imposed by the physics of absorption and pressure drop limits; both of which are captured via experimentally deduced empirical correlations. The results show that the minichannel absorbers are economically competitive to conventional systems for low capacity CO₂ capture achieving savings ranging from ～50% to 3% for plant capacities ranging from 5 to 50 MMSCFD, respectively, primarily due to their lower capital costs. At higher plant capacities, the higher operating costs of the minichannel units dominate their NPVC and as such lead them to lose their competitiveness. © 2017 American Institute of Chemical Engineers AIChE J, 64: 620–631, 2018     

Influence of firing conditions and production methods on fracture strength of titanium-based metal ceramic crowns

Objectives: This study evaluated the effect of argon atmosphere compared with vacuum during porcelain firing on the fracture strength of crowns made of porcelain and electron beam melted (EBM) Ti-6Al-4 V, cast commercially pure titanium or milled commercially pure titanium. Methods: Sixty crown copings of c. p. titanium, Ti-6Al-4 V alloy and porcelain were fabricated using three production techniques. The copings were fired either under vacuum or in an argon gas atmosphere. Specimens were subdivided into groups of cast c. p. titanium, milled c. p. titanium and EBM Ti-6Al-4 V which were further subdivided according to firing modes employing either vacuum or argon gas. The 60 specimens were subjected to cyclic preloading and thermocycling, and were then individually loaded until interface fractured. Differences between the group mean values were calculated using the one-way ANOVA and Tukey’s range test. Two fractured samples from each group were cut with a diamond blade and examined using SEM and EDS for visualization and chemical composition analysis of the fractured interface. Results: The highest mean fracture strength values, though not significant, were recorded for the groups fired in argon atmosphere, and the lowest mean fracture strength values were recorded for the groups fired in vacuum, with one exception. Comparing the two main groups of firing atmosphere, no significant difference could be documented. SEM and EDS analysis indicated clear differences in composition and structure between the groups included in the study. Conclusions: Firing in argon atmosphere does not significantly improve the fracture strength of porcelain bonded to titanium.     

Evaluation of Nitrogen Fixing Enzyme Activities in Response to Pyrene Bioremediation Efficacy by Defined Artificial Microalgal-Bacterial Consortium of Gujarat,India

This study was carried out to investigate the response and relationship between nitrogen fixing enzymes during the remediation of different concentrations of high molecular weight four rings Polynuclear Aromatic Hydrocarbon (PAH) Pyrene by microalgae Synechocystis sp. (cyanobacteria) with artificial developed indigenous bacterial consortium. One axenic microalgal culture of Synechocystis sp. and two pyrene degrading indigenous bacteria with efficient removal capabilities viz. Pseudomonas indoxyladons and Bacillus benzoevorans isolated from crude oil polluted site and common industrial effluent canal were used to construct the consortium. The effect of pyrene on algal growth in terms of chlorophyll-a was measured and it was found that in the presence of bacteria, the growth and bioremediation capacity of Synechocystis sp. raised tremendously, whereas Synechocystis sp. monoculture exhibited concentration dependent decrease. Moreover, the nitrogen fixing enzymes; nitrate reductase (NR), glutamine synthetase (GS), and succinate dehydrogenase (SDH) showed chronological decrease by 93%, 90%, and 98%, respectively. Increased Bioremediation of pyrene by consortium JPNKA7B2 (Mix culture of Synechocystis sp., Pseudomonas indoxyladons, and Bacillus benzoevorans) was eliminated at 94.1% in 50 mg/L, which indirectly retarded the nitrogen fixing enzymes – NR, GS, and SDH. However, Synechocystis sp. monoculture could remediate up to 36% at 1.5 mg/L after 16 days of incubation.     

Kinetics of short‐duration ethylene polymerization with MgCl2‐supported Ziegler–Natta catalyst: Two‐stage initiation evidenced by changes in active center concentration

The kinetics of ethylene polymerization with a TiCl₄/MgCl₂‐type Ziegler–Natta catalyst was studied. Changes in polymerization activity and concentration of active centers ([C*]) in the first 5 min were determined. Initiation of the active centers was found to proceed in two stages. In the first stage, [C*]/[Ti] quickly rose to about 1% in less than 30 s and then remained stable in the subsequent 60 s. Then the [C*]/[Ti] value started to increase again, forming the second buildup stage. The polymerization activity was found to change roughly in parallel with the change in [C*]/[Ti]. Changes in the polymer/catalyst particle morphology and polymer molecular weight distribution with polymerization time were studied. A mechanistic model was proposed to explain the two‐stage kinetics: initiation of active sites on the outer surface of catalyst particles takes place in the first stage, and initiation of active sites buried inside the particles takes place in the second stage. These buried sites are released when the catalyst particles are fragmented by the expanding polymer phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45187.     

Polypropylene/multiwall carbon nanotubes nanocomposites: Nanoindentation,dynamic mechanical,and electrical properties

Polypropylene (PP)/Multiwall carbon nanotubes (MWCNTs) nanocomposites were fabricated via melt compounding that utilizes a corotating twin‐screw extruder. Two commercially available MWCNTs, Baytubes C150P and C70P, were incorporated into PP matrix at concentration of 3 wt %. The nanocomposites samples were analyzed using scanning electron microscopy, dynamic mechanical analysis (DMA), nanoindentation test, and picoammeter. It was found that both MWCNTs types were well distributed and dispersed in the PP matrix and no agglomeration of MWCNTs was observed. The DMA analysis results showed that the incorporation of MWCNTs enhanced the storage modulus and thermal stability of the PP matrix. Whereas, nanoindentation creep results showed that the creep rate and displacement of the PP/MWCNTs nanocomposites was lower than the neat PP, in which C70P < C150P < PP. The reduction of creep rate and creep displacement was associated to the improvement of creep resistance. There were also improvements on hardness and stiffness of the nanocomposites. Additionally, the electrical resistivity of the neat PP decreased with the incorporation of MWCNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45293.     

Kinetics of oxidative cracking of n‐hexane to olefins over VOx/Ce‐Al2O3 under gas phase oxygen‐free environment

The kinetics of oxidative cracking of n‐hexane to olefins using lattice oxygen of VO_x/Ce‐Al₂O₃ is investigated. The TPR/TPO analysis shows a consistent reducibility (79%) of VO_x/Ce‐Al₂O₃ in repeated redox cycles. The total acidity of the sample is found to be 0.54 mmol/g with 22% are strong acid sites that favors olefin selectivity. The oxidative cracking of n‐hexane in a fluidized CREC Riser simulator gives approximately 60% olefin selectivity at 30% n‐hexane conversion. A kinetic model is developed considering (1) cracking, (2) oxidative dehydrogenation (ODH), and (3) catalyst deactivations. The proposed cracking mechanism considers adsorption, C–H and C–C bond fission and desorption as elementary steps and implemented by pseudo steady state hypothesis. A Langmuir‐Hinshelwood mechanism is found to represent the ODH reactions. The developed model fits the experimental data with favorable statistical indicators. The estimated specific reaction rate constants are also found to be consistent with the product selectivity data. © 2016 American Institute of Chemical Engineers AIChE J, 63: 130–138, 2017     

Recent advancements in bioreactions of cellular and cell-free systems: A study of bacterial cellulose as a model

Conventional approaches of regulating natural biochemical and biological processes are greatly hampered by the complexity of natural systems. Therefore, current biotechnological research is focused on improving biological systems and processes using advanced technologies such as genetic and metabolic engineering. These technologies, which employ principles of synthetic and systems biology, are greatly motivated by the diversity of living organisms to improve biological processes and allow the manipulation and reprogramming of target bioreactions and cellular systems. This review describes recent developments in cell biology, as well as genetic and metabolic engineering, and their role in enhancing biological processes. In particular, we illustrate recent advancements in genetic and metabolic engineering with respect to the production of bacterial cellulose (BC) using the model systems Gluconacetobacter xylinum and Gluconacetobacter hansenii. Besides, the cell-free enzyme system, representing the latest engineering strategies, has been comprehensively described. The content covered in the current review will lead readers to get an insight into developing novel metabolic pathways and engineering novel strains for enhanced production of BC and other bioproducts formation.     

All-digital gated ring oscillator $$\Delta \Sigma$$ modulators

This paper presents all-digital time-mode \(\Delta \Sigma\) modulators. The proposed modulators consist of a voltage-to-time integrator, a seven-stage gated ring oscillator functioning as a 3-bit quantizer, and seven digital differentiators. A detailed analysis of the nonlinear characteristics of the modulators is provided. Designed in IBM 130 nm 1.2 V CMOS technology with a 100 mV 100 kHz sinusoidal input and a 4.4 MHz frequency clock, the first-order modulator provides 47 dB SNR over 0–150 KHz bandwidth while consuming 1.1 mW while the second-order modulator provides 55 dB SNR over the same bandwidth while consuming consumes 1.45 mW.     

Effect of various surface preparation techniques on the delamination properties of vacuum infused Carbon fiber reinforced aluminum laminates (CARALL): Experimentation and numerical simulation

Carbon fiber reinforced aluminum laminates (CARALL) are one of the aluminum based Fiber metal laminates (FMLs) which, due to their high strength to weight ratio and good impact resistance are greatly replacing aluminum alloys in aircraft structures. In this research work, interlaminate shear strength of Vacuum assisted resin transfer molding (VARTM) manufactured CARALL has been investigated. Numerical simulation model incorporated with real time material data has been developed to predict the delamination behavior of CARALL laminates. Standard CARALL specimens with different surface morphologies were prepared by electric discharge machining, mechanical, chemical and electrochemical surface treatments. T-peel tests were carried out according to standard ASTM D1876-08 to find out inter laminate shear strength. FMLs made out of mechanically, chemically and electrochemically cleaned metal sheets depicted high interlaminate shear strength. SEM micrographs of failed surfaces verify the high adhesive strength of epoxy. Developed numerical simulation model accurately predicts the delamination behavior of CARALL as observed during experimentation.     

Job search website for illiterate users of Pakistan

Illiteracy is a major hurdle in socio-economic development of Pakistan. Research in the Information and Communication Technology (ICT) can help in tackling this issue by developing solutions tailored for illiterate population. The work presented within this paper proposes a job search website for illiterate population of KPK province of Pakistan. The designed website does not require any human assistance while searching a job. Moreover, the website uses culturally relevant graphical and audio content. The usability of the website is tested according to the ISO-9241-11 specification. Furthermore, we have studied the effect of the participants’ characteristics, i.e., their age, computer and mobile usage experience on the usability of the website. The results show that the participants found the website usable. Specifically, they could search suitable jobs with a minimal number of clicks and in less time as compared to the usual task completion rates reported throughout the literature. None of the participants’ characteristics were found to be affecting the usability of the website. These results suggest a promising potential of ICT solutions for providing services to illiterate population of Pakistan.