Impact behavior of aminosilane functionalized nanosilica based shear thickening fluid impregnated Kevlar fabrics

In the present work, two types of shear thickening fluids have been synthesized by using neat and aminosilane functionalized silica nanoparticles and their viscosity curves have been obtained by the rheometer. Based on the values of peak viscosity of synthesized shear thickening fluids, the surface functionalized nanosilica based shear thickening fluid has been chosen as a best candidate due to the high viscosity for impregnation into the neat Kevlar of different layers viz. four (04) and eight (08) layers for velocity impact study. The experimental investigations reveal high energy absorption of shear thickening fluid impregnated Kevlar as compared to the neat Kevlar. The maximum energy absorption 62 J is achieved corresponding to the initial velocity 154 m∙s⁻¹ for 08 layers shear thickening fluid impregnated Kevlar specimen. The data have also been analytically determined and validated with the experimental data. The experimental data have good agreement with the analytical data within the accuracy of around 15 to 20%. The present findings can have significant inferences towards the fabrication of shear thickening fluids using nanomaterials for numerous applications such as soft armors, dampers, nanofinishing and so forth.     

Chitosan-based magnetic molecularly imprinted polymer: synthesis and application in selective recognition of tricyclazole from rice and water samples

A tricyclazole selective chitosan/Fe₃O₄ magnetic molecularly imprinted polymer (MMIP) was synthesized using non-covalent binding polymerization involving methacrylic acid (MAA) as functional monomer, divinylbenzene (DVB-80) as crosslinker, 2,2'-azobisisobutyronitrile as initiator, acetonitrile/toluene (75:25, v/v) as porogenic solvent and tricyclazole as template. Surface morphology and magnetic characterization of the prepared imprinted and non-imprinted polymers were done using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry and vibrating sample magnetometry, respectively. The adsorption kinetic data fitted best in pseudo-second-order model. The adsorption equilibrium was achieved in 30 min and the maximum binding capacity was 4579.9 µg/g. The Freundlich isotherm model was found suitable for explaining the binding isotherm data (R² > 0.99). Negative values of thermodynamic parameters ∆G (Gibb’s free energy), ∆H (enthalpy), and ∆S (entropy) revealed exothermic and spontaneous nature of adsorption processes. It also revealed decreased randomness at the solid–liquid interface during sorption. The scatchard plot analysis suggested heterogeneity of binding sites on MMIPs. The molecular recognition selectivity of MMIPs towards tricyclazole was much higher, as compared to its structural analogues, tebuconazole (α = 28.58) and hexaconazole (α = 37.16). The MMIPs were successfully applied to separate and enrich tricyclazole from fortified samples of rice and water, with a recovery percentage of 89.4% and 90.9%, respectively. These reusable imprinted polymers possessing high selectivity and specificity can be utilized as an adsorbent for solid-phase extraction in sample preparation for tricyclazole residue analysis in complex environmental matrices.

     

Harmony search algorithm for infinite impulse response system identification

In this paper, optimal sets of filter coefficients are searched by a meta-heuristic optimization technique called Harmony Search (HS) algorithm for infinite impulse response (IIR) system identification problem. For different optimization problems, HS algorithm undergoes three basic rules; namely Random Selection (RS), Harmony Memory Consideration (HMC), and Pitch Adjustment (PA) rules, which are inspired from the process that the musicians use to improvise a perfect state of harmony with the consummate skill of blending notes in tune. With the help of the properly selected control parameters, a perfect balance is achieved in exploration and exploitation in searching phases. The detailed analysis of simulation results emphasizes the strength of HS algorithm to find the near-global optimal solution, quality of convergence profile and the speed of convergence while tested against standard benchmark examples for same and reduced order models.     

Sand corrosion,thermal expansion,and ablation of medium- and high-entropy compositionally complex fluorite oxides

Sand corrosion, thermal expansion, and ablation properties of a new class of medium- and high-entropy compositionally complex fluorite oxides (CCFOs) are examined as potential protective coating materials. Five binary oxides were mixed and sintered into dense, single-phase CCFOs of the general formula: [Hf_(1-2x)/3Zr_(1-2x)/3Ce_(1-2x)/3Y_xYb_x]O_2-δ (x = 0.2, 0.074, and 0.029). These CCFOs exhibit decreased molten sand infiltration and interaction at intermediate temperatures (1200-1300°C) in comparison with a cubic yttria-stabilized zirconia (YSZ) reference; however, at higher temperatures, the trend is reversed due to the increased chemical reactivity. The equimolar high-entropy (Hf_0.2Zr_0.2Ce_0.2Y_0.2Yb_0.2)O_2-δ exhibits no grain boundary penetration by molten sand at all examined temperatures (1200°C-1500°C), although reaction and precipitation are significant. Moreover, these CCFOs exhibit higher intrinsic thermal expansion coefficients (CTE) than the YSZ reference, thereby being more compatible with Ni-based superalloys. The 8YSZ-like (Hf_0.284Zr_0.284Ce_0.284Y_0.074Yb_0.074)O_2-δ exhibits the highest CTE in this series of CCFOs due to oxygen clustering effects. Finally, these CCFOs also exhibit lower emissivities and form unique faceted microstructures in ablative environments.     

Application of evolutionary optimization techniques for finding the optimal set of concentric circular antenna array

In this paper the maximum sidelobe level (SLL) reductions, optimal beam patterns and optimal beam widths of various designs of three-ring planar concentric circular antenna arrays (PCCAA) are examined using three different classes of evolutionary optimization techniques to finally determine the global optimal three-ring PCCAA design and then establish some sort of ranking among the techniques. Apart from physical construction of a PCCAA, one may broadly classify its design into two major categories: uniformly excited arrays and non-uniformly excited arrays. The present paper assumes non-uniform excitations and uniform spacing of excitation elements in each three-ring PCCAA design and a design goal of maximizing SLL reduction associated with optimal beam patterns and beam widths. The design problem is modeled as an optimization problem for each PCCAA design and solved using different evolutionary optimization techniques to determine an optimum set of normalized excitation weights for PCCAA elements, which, when incorporated, results in a radiation pattern with optimal (maximum) SLL reduction. Among the various PCCAA designs, one which yields the global minimum SLL with global minimum first null beamwidth is the global optimal design. In this work the three-ring PCCAA containing (N₁ = 4, N₂ = 6, N₃ = 8) elements proves to be such global optimal design. The optimization techniques employed are real coded GA (RGA), canonical PSO (CPSO), craziness based PSO (CRPSO), evolutionary programming (BEP), hybrid evolutionary programming (HEP). While ranking the techniques after 30 total runs for each design, HEP, CRPSO, RGA, CPSO, BGA hold the first five ranks in order of optimization capability. HEP yields global minimum SLL (?32.86 dB) and global minimum BWFN (77.0°) for the optimal design. BEP often changes the rank from second to fifth depending on the design set. Further, when compared to a uniformly excited PCCAA having equal number of elements and same radii a reduction of major lobe beamwidth is also observed in the optimal non-uniformly excited case.     

Polyacrylonitrile solution homogeneity study by dynamic shear rheology and the effect on the carbon fiber tensile strength

Poly(acrylonitrile‐co‐methacrylic acid) (PAN‐co‐MAA)/N,N‐dimethylformamide (DMF) solutions were prepared and dynamic shear rheology of these solutions were investigated. With increasing stirring time up to 72 h at 70°C, the polymer solution became less elastic (more liquid‐like) with a ～60% reduction in the zero‐shear viscosity. Relaxation spectra of the PAN‐co‐MAA/DMF solutions yield a decrease in relaxation time (disentanglement time, τ_d), corresponding to an about 8% decrease in viscosity average molecular weight. The log‐log plot of G′ (storage modulus) versus G″ (loss modulus) exhibited an increase in slope as a function of stirring time, suggesting that the molecular level solution homogeneity increased. In order to study the effect of solution homogeneity on the resulting carbon fiber tensile strength, multiple PAN‐co‐MAA/DMF solutions were prepared, and the precursor fibers were processed using gel‐spinning, followed by continuous stabilization and carbonization. The rheological properties of each solution were also measured and correlated with the tensile strength values of the carbon fibers. It was observed that with increasing the slope of the G′ versus G″ log‐log plot from 1.471 to 1.552, and reducing interfilament fiber friction during precursor fiber drawing through the addition of a fiber washing step prior to fiber drawing, the carbon fiber strength was improved (from 3.7 to 5.8 GPa). This suggests that along with precursor fiber manufacturing and carbonization, the solution homogeneity is also very important to obtain high strength carbon fiber. POLYM. ENG. SCI., 56:361–370, 2016. © 2016 Society of Plastics Engineers     

Solid‐state NMR study of spin finish of thermally treated PAN and PAN/CNT precursor fibers

Dry‐jet wet‐spun polyacrylonitrile (PAN) and PAN/carbon nanotubes (CNTs) precursor fibers coated by spin finishes were characterized using the solid‐state ¹H nuclear magnetic resonance technique. Series of fiber samples were prepared upon thermal treatment at different temperatures (room temperature to 180°C). Using the Hahn echo sequence, relatively mobile components were identified and the effect of the heat treatment on those components was studied. It was observed that the mobile components are mainly the spin finishes. Heat treatment caused loss of one of the spin finishes (Type B) to a great extent (～80%), whereas the other two spin finishes (Type A and Type C) were more stable. Additional information regarding the change in molecular mobility due to heat treatment was obtained by the spin‐lattice relaxation time ( T₁ ) analysis. It was found that the presence of CNT affects the T₁ relaxation time of the polymer in the composite fiber, however, that of relatively mobile components remains unaffected. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40734.     

Coordinated control of TCPS and SMES for frequency regulation of interconnected restructured power systems with dynamic participation from DFIG based wind farm

Among the several wind generation technologies, variable-speed wind turbines utilizing doubly fed induction generators (DFIG) are gaining momentum in the power industry. Increased penetration of these wind turbine generators displaces conventional synchronous generators which results in erosion of system frequency. With this assertion, the paper analyzes the dynamic participation of DFIG for frequency control of an interconnected two-area power system in restructured competitive electricity market. Frequency control support function responding proportionally to frequency deviation is proposed to take out the kinetic energy of wind turbine for improving the frequency response of the system. Impacts of varying wind penetration in the system and varying active power support from DFIG on frequency control have been investigated. The presence of thyristor controlled phase shifter (TCPS) in series with the tie-line and Superconducting Magnetic Energy Storage (SMES) at the terminal of one area in conjunction with dynamic active power support from DFIG results in optimal transient performance for PoolCo transactions. Integral gains of AGC loop and parameters of TCPS and SMES are optimized through craziness-based particle swarm optimization (CRPSO) in order to have optimal transient responses of area frequencies, tie-line power deviation and DFIG parameters.     

Whole Body Ip6k1 Deletion Protects Mice from Age-Induced Weight Gain,Insulin Resistance and Metabolic Dysfunction

(1) Background: We previously demonstrated that disruption of IP6K1 improves metabolism, protecting mice from high-fat diet-induced obesity, insulin resistance, and non-alcoholic fatty liver disease and steatohepatitis. Age-induced metabolic dysfunction is a major risk factor for metabolic diseases. The involvement of IP6K1 in this process is unknown. (2) Methods: Here, we compared body and fat mass, insulin sensitivity, energy expenditure and serum-, adipose tissue- and liver-metabolic parameters of chow-fed, aged, wild type (aWT) and whole body Ip6k1 knockout (aKO) mice. (3) Results: IP6K1 was upregulated in the adipose tissue and liver of aWT mice compared to young WT mice. Moreover, Ip6k1 deletion blocked age-induced increase in body- and fat-weight and insulin resistance in mice. aKO mice oxidized carbohydrates more efficiently. The knockouts displayed reduced levels of serum insulin, triglycerides, and non-esterified fatty acids. Ip6k1 deletion partly protected age-induced decline of the thermogenic uncoupling protein UCP1 in inguinal white adipose tissue. Targets inhibited by IP6K1 activity such as the insulin sensitivity- and energy expenditure-inducing protein kinases, protein kinase B (PKB/Akt) and AMP-activated protein kinase (AMPK), were activated in the adipose tissue and liver of aKO mice. (4) Conclusions: Ip6k1 deletion maintains healthy metabolism in aging and thus, targeting this kinase may delay the development of age-induced metabolic dysfunction.     

A computer simulation approach to evaluating bowl versus inverted bowl assembly line arrangement with variable operation times

A computer simulation model was used to evaluate a bowl versus inverted bowl assembly line arrangement for normal and exponential distributions and variances equal to 1 and 16. The model was developed on the basis of a realistic case problem and applied to a six-station assembly line. The results show that the inverted bowl is superior to the bowl arrangement for a normal distribution in terms of the total elapsed time evaluation criterion; however, with an exponential distribution, the bowl was found better than the inverted bowl for the same criterion. On the basis of the average percentage of working time and the average time in the system evaluation criteria, the bowl was found superior to the inverted bowl for a normal distribution. Similar results were obtained for an exponential distribution with a variance equal to 1, but no definitive inference could be made with a variance equal to 16.