Rheological behavior of polypropylene nanocomposites with tailored polymer/multiwall carbon nanotubes interface

Maleic anhydride grafted polypropylene (MA‐g‐PP) or polypropylene (PP) was noncovalently coated onto acid functionalized multiwall carbon nanotube (f‐MWNT) through solution mixing. These coated f‐MWNTs and pristine MWNT (p‐MWNT) were melt microcompounded with neat PP to form PP/f‐MWNT and PP/p‐MWNT nanocomposites at 0.1–1 wt% MWNT concentration. Complex viscosity and tan δ (ratio of loss modulus to storage modulus) behavior of these systems were studied using dynamic frequency sweep test, while relaxation time, activation energy, and melt homogeneity were also calculated and compared. Among the three types of samples, PP/f‐MWNT masterbatch‐based nanocomposite demonstrated not only the presence of interphase but also good processability. As a consequence, increase of both the crystallization rate in the presence of shear and the melt elasticity during annealing were found only in the masterbatch‐based samples but not in the PP/p‐MWNT. The mechanism of such increased melt elasticity was attributed to the formation of the space‐spanning network, which is consistent with the Cole–Cole plot showing similar behavior to the branched polymers in the literature. This has implications in polymer processing due to suggested changes in the balance between melt strength and polymer flow. Nanocomposite rheological behavior has also been correlated with the mechanical properties. POLYM. ENG. SCI., 59:1763–1777, 2019. © 2019 Society of Plastics Engineers     

Micellar solubilization of naphthalene and phenanthrene from nonaqueous-phase liquids

The equilibrium partitioning of the polycyclic aromatic hydrocarbon (PAH) compounds naphthalene and phenanthrene, from nonaqueous-phase liquids (NAPLs) into micellar solutions of five different nonionic polyethoxylated surfactants, is evaluated in this study. A series of synthesized NAPLs, comprised of naphthalene and/or phenanthrene dissolved in hexadecane at varying concentrations, were equilibrated with surfactant solutions in well-mixed batch systems. It was observed that the extent of micellar partitioning of PAH compounds increases linearly with their relative abundance in the NAPLs. A theoretical liquid-liquid partitioning framework that describes PAH equilibrium partitioning between the NAPL, aqueous, and the liquid-like micellar phases is presented. Although the maximum solubilization capacity of micelles is generally higher for naphthalene as compared to phenanthrene, results indicate that with certain NAPLs phenanthrene may be solubilized to a similar extent as naphthalene, even when equal mole fractions of the compounds are present in the NAPLs. Selective solubilization of naphthalene over phenanthrene into micellar solutions of Brij 35 was observed in systems where naphthalene and phenanthrene were both present. The extent of micellar partitioning of phenanthrene was decreased by approximately 18% in the presence of naphthalene, while naphthalene partitioning was unaffected by the presence of phenanthrene.     

Characterization of delamination effect on composite laminates using a new generalized layerwise approach

A dynamic analysis method has been developed to investigate and characterize the effect due to presence of discrete single and multiple embedded delaminations on the dynamic response of composite laminated structures with balanced/unbalanced and arbitrary stacking sequences in terms of number, placement, mode shapes and natural frequencies. A new generalized layerwise finite element model is developed to model the presence of multiple finite delamination in laminated composites. The new theory accurately predicts the interlaminar shear stresses while maintaining computational efficiency.     

Intelligent particle swarm optimized fuzzy PID controller for AVR system

In process plants like thermal power plants, biomedical instrumentation the popular use of proportional-integral-derivative (PID) controllers can be noted. Proper tuning of such controllers is obviously a prime priority as any other alternative situation will require a high degree of industrial expertise. So in order to get the best results of PID controllers the optimal tuning of PID gains is required. This paper, thus, deals with the determination of off-line, nominal, optimal PID gains of a PID controller of an automatic voltage regulator (AVR) for nominal system parameters and step reference voltage input. Craziness based particle swarm optimization (CRPSO) and binary coded genetic algorithm (GA) are the two props used to get the optimal PID gains. CRPSO proves to be more robust than GA in performing optimal transient performance even under various nominal operating conditions. Computational time required by CRPSO is lesser than that of GA. Factors that have influenced the enhancement of global searching ability of PSO are the incorporation of systematic and intelligent velocity, position updating procedure and introduction of craziness. This modified from of PSO is termed as CRPSO. For on-line off-nominal system parameters Sugeno fuzzy logic (SFL) is applied to get on-line terminal voltage response. The work of SFL is to extrapolate intelligently and linearly, the nominal optimal gains in order to determine off-nominal optimal gains. The on-line computational burden of SFL is noticeably low. Consequently, on-line optimized transient response of incremental change in terminal voltage is obtained.     

Interaction characteristics and thermodynamic behaviour of gatifloxacin by aluminium hydroxide

The interaction pattern of gatifloxacin was temperature-dependent Langmuir isotherm, and the Langmuir coefficients increased as the temperature was raised. The perturbation experiment conducted on this system showed that the nature of interaction was irreversible. The enthalpy change is a positive value, indicating the existence of increased activation energy as the temperature is raised. The entropy value, 24.21 e.u. obtained in this system, indicated that the hydration shells of the ions were rather tightly bound. Intestinal permeation study also revealed the decreased bioavailability of gatifloxacin relatively to the presence of aluminium hydroxide. The strong adsorption of gatifloxacin by aluminium hydroxide is due to formation of complexes with cations of aluminium hydroxide through carboxyl and carbonyl groups of gatifloxacin.     

Optimal sizing and design of CMOS analogue amplifier circuits using craziness‐based particle swarm optimization

This paper presents the optimal designs of two analogue complementary metal–oxide–semiconductor (CMOS) amplifier circuits, namely differential amplifier with current mirror load and two‐stage operational amplifier. A modified Particle Swarm Optimization (PSO), called Craziness‐based Particle Swarm Optimization (CRPSO) technique is applied to minimize the total MOS area of the designed circuits. CRPSO is a highly modified version of conventional PSO, which adopts a number of random variables and has a better and faster exploration and exploitation capability in the multidimensional search space. Integration of craziness factor in the fundamental velocity term of PSO not only brings diversity in particles but also pledges convergence close to global best solution. The proposed CRPSO‐based circuit optimization technique is reassured to be free from the intrinsic disadvantages of premature convergence and stagnation, unlike Differential Evolution (DE), Harmony Search (HS), Artificial Bee Colony (ABC) and Particle Swarm Optimization (PSO). The simulation results achieved for the two analogue CMOS amplifier circuits establish the efficacy of the proposed CRPSO‐based approach over those of DE, HS, ABC and PSO in terms of convergence haste, design conditions and design goals. The optimally designed analogue CMOS amplifier circuits occupy the least MOS area and show the best performance parameters like gain and power dissipation, in compared with the other reported literature. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of maleic anhydride grafted polypropylene on the mechanical and morphological properties of chemically modified short‐pineapple‐leaf‐fiber‐reinforced polypropylene composites

With the rising cost of petroleum‐based fibers, the utilization of plant fibers in the manufacture of polymer–matrix composites is gaining importance worldwide. The scope of this study was to examine the perspective of the use of pineapple leaf fibers (PALFs) as reinforcements for polypropylene (PP). These fibers are environmentally friendly, low‐cost byproducts of pineapple cultivation and are readily available in the northeastern region of India. Here, both untreated and treated pineapple fibers were used. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizing agent. The polymer matrix of PP was used to prepare composite specimens with different volume fractions (5–20%) of fibers by the addition of 5% of MA‐g‐PP. These specimens were tested for their mechanical properties, and additional assessments were made via observations by scanning electron microscopy, thermogravimetric analysis, and IR spectroscopy. Increase in the impact behavior, flexural properties, and tensile moduli of the composites were noticed, and these were more appreciable in the treated fibers mixed with MA‐g‐PP. PALF in 10 vol % in PP mixed with MA‐g‐PP was the optimum and recommended composition, where the flexural properties were the maximum. The impact strength and the tensile modulus were also considerably high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

On properties of state variable stabilizing feedback of a special kind for linear time-invariant regulators

Some interesting properties of a limiting case of linear optimal regulators with quadratic performance index and prescribed degree of stability are discussed. A series of LSVF control laws may be generated by varying a scalar parameter α which specifies the minimum modulus of the real part of the closed-loop poles. All such control laws guarantee a minimum amount of phase and gain margins but differ in speed of error recovery. Explicit algebraic relations for computing feedback laws and Nyquist plots are provided for single inputn-order systems.     

A hybrid backtracking search algorithm with wavelet mutation-based nonlinear system identification of Hammerstein models

In this paper a novel and accurate approach is presented to identify varieties of nonlinear Hammerstein models (closed loop and open loop) with the help of an optimization algorithm that combines a recently proposed backtracking search algorithm with wavelet theory-based mutation scheme (BSA-WM). The optimum output MSE associated with each plant along with its statistical information justifies the better precision and accuracy of BSA-WM-based identification approach as compared to the other methods reported in earlier literature.     

Incorporating quantitative reliability engineering measures into tradespace exploration

Recently, tradespace analysis and exploration has emerged as an important focus area within the Department of Defense Engineered Resilient System initiative, which draws upon engineering concepts, science, and design tools to produce trusted and effective solutions for a wide range of operational contexts. Most of the previous research on tradespace analysis, including those developed for rotorcraft, emphasize performance. However, non-functional requirements such as reliability, availability, and maintainability have received minimal consideration, despite their direct influence on program level concerns such as operation and support as well as affordability. This paper proposes a strategy to incorporate reliability engineering into tradespace analysis. We also develop a subsystem-level reliability investment model that is illustrated through a simplified example. Our results suggest that reliability investment could achieve significant savings over a systems lifecycle, thereby enabling improved fleet availability and a larger fleet size.