Effect of Solvent on Segregated Network Morphology in Elastomer Composites for Tunable Piezoresistivity

Flexible, light‐weight, and wearable electronics have significant potential for the development of Internet of Things. Flexible sensors with tunable piezoresistive properties are in high demand for various practical applications. Herein, different morphology thermoplastic polyurethane (TPU)/ carbon nanostructure (CNS) composites with segregated network are obtained by swelling the TPU powders using various solvents. The better solvent for TPU, dimethylformamide (DMF), renders the composites with 0.7 wt% CNS stronger polymer‐filler interactions, resulting in significantly improved piezoresistive sensitivity at strain larger than 150%. Also the gauge factors (G_Fs) for these composites are 9.7 in the range 0–60% strain and 19.3 for 60–100% strain. In contrast, the composites with ethanol (EtOH) and tetrahydrofuran (THF) which swell less the TPU show delayed increase in piezoresistivity and G_Fs of 2.2 and 3.5 for strain up to 100%, respectively, suggesting potential applications for stretchable conductors.     

Use of maleic anhydride–grafted polyethylene as compatibilizer for HDPE–tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol‐plasticized and in unplasticized states was blended with high‐density polyethylene (HDPE) using HDPE‐g‐maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact‐fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 863–872, 2001     

Effect of carbon nanotube dispersion and network formation on thermal conductivity of thermoplastic polyurethane/carbon nanotube nanocomposites

Carbon nanotubes (CNTs) were dispersed without any solvent in poly(tetramethylene ether glycol), (PTMEG) well above its melting point by ultrasonication in the pulse mode and different times. The polyol/CNT suspensions were used to prepare in situ polymerized thermoplastic polyurethane TPU/CNT nanocomposites with the CNT concentration of ～ 0.05 vol%, much below the CNT geometrical percolation threshold calculated at 0.43 vol%. Results of rotational rheological measurements and ultraviolet–visible (UV‐Vis) spectroscopy analysis revealed improvement in the nanoscale CNT dispersion with sonication time. Moreover, the optical microscopic images and sedimentation behavior for these samples pointed out to the formation of segregated CNT networks with different microstructures at different sonication times. Through‐plane thermal conductivity measurements showed an increase in thermal conductivity of the in‐situ polymerized TPU/CNT nanocomposites from polyol/CNT suspensions with increasing sonication time followed by a decrease at long sonication times. Different models were used to evaluate the role of CNT dispersion state and created microstructure on thermal conductivity of nanocomposites. The formation of a segregated network at medium sonication times consisting of large CNT aggregates and small bundles increased the nanocomposite thermal conductivity up to 99.7%, while at longer sonication times, an increase in interfacial area with a corresponding increase in kapitza boundary resistance, effectively decreased the system thermal conductivity. POLYM. ENG. SCI., 56:394–407, 2016. © 2016 Society of Plastics Engineers     

Illumination normalized based technique for retinal blood vessel segmentation

The Retinal image carries important information about the health of the sensory part of the visual system. In this paper, a new approach is suggested by utilizing the homomorphic filter integrated with Contrast limited adaptive histogram equalization (CLAHE) method for the illumination normalization and contrast enhancement of the retinal images. Then segmentation is done through several steps by using the existing methods such as morphological filtering, a second derivative operator that is followed by a final morphological filtering stage and hysteresis thresholding. The suggested method is verified on DRIVE and CHASE‐DB1 databases and has average accuracy of 72.03% and 64.54%, accordingly. The obtained results demonstrate that the proposed approaches achieve higher accuracy than the traditional method. The suggested approach not only contributes to the successful result, but also minimizes the computing time.     

A novel smart hybrid-Trefftz finite element for smart laminated composite plates

A novel smart hybrid-Trefftz finite element ( HTFE ) has been developed for the analysis of smart laminated composite plates. The substrates of the smart plates are symmetric and antisymmetric cross-ply plates. The derivation of this HTFE is devoid of the complicated task of finding the particular solutions of simultaneous governing partial differential equations. The Trefftz functions are constructed from the finite number of free-field exact solutions of the homogeneous simultaneous governing partial differential equations of the element domain in a straightforward manner without transforming them into a single governing equation. The HTFE is validated with the exact solutions of the smart composite plates. It is observed that this HTFE is an efficient finite element and can be utilized for the analysis of active control of smart composite structures.     

Oxidation of aqueous sulfur dioxide catalyzed by poly-4-vinylpyridine–Cu(II) complex. Part 1: Homogeneous phase oxidation

The oxidation of aqueous sulfur dioxide in the presence of polymer-supported copper(II) catalyst is also accompanied by homogeneous oxidation of aqueous sulfur dioxide catalyzed by leached copper(II) ions. Aqueous phase oxidation of sulfur dioxide of low concentrations by oxygen in the presence of dissolved copper(II) has therefore been studied. The solubility of SO₂ in aqueous solutions is not affected by the concentration of copper(II) in the solution. In the oxidation reaction, only HSO is the reactive S(IV) species. Based on this observation a rate model which also incorporates the effect of sulfuric acid on the solubility of SO₂ is developed. The rate model includes a power-law type term for the rate of homogeneous phase reaction obtained from a proposed free-radical chain mechanism for the oxidation. Experiments are conducted at various levels of concentrations of SO₂ and O₂ in the gas phase and Cu(II) in the liquid phase. The observed orders are one in each of O₂, Cu(II) and HSO. This suggests a first-order termination of the free radicals of bisulfite ions.     

Impurity modulated excitation profile of doped quantum dot subject to oscillatory magnetic field

We explore the excitation profile of a repulsive impurity doped quantum dot under periodically fluctuating magnetic field. We have considered Gaussian impurity centers. The investigation reveals the roles subtly played by the dopant coordinate and the region of influence of the dopant to modulate the excitation pattern. The rate of transition to the excited states has been invoked to analyze the interplay between the above two impurity parameters in influencing the excitation process. The ratio of cyclotron frequency and harmonic confinement potential has important impact on excitation rate.     

Differential superhydrophobicity and hydrophilicity on a thin cellulose layer

Here we have developed cellulosic materials (cotton fabric or paper) with differential superhydrophobicity and hydrophilicity on each side of the surfaces by coating with polyvinylidene fluoride and fluorinated silane molecules using electro-spraying. Such materials are advantageous in various textile and medical applications.Analysis of surface morphology indicated that, not only surface chemical property and roughness, but also particle diameter affects surface superhydrophobicity. Smaller particle diameter enhances superhydrophobicity, if the surface roughness and surface chemical property remain constant. By controlling these three factors, superhydrophobicity with a water contact angle of more than 160° can be achieved at one side of a thin cellulosic material while maintaining the hydrophilicity (contact angle is 0°) at the opposite side.     

Energy Efficient Reliable Multi-path Data Transmission in WSN for Healthcare Application

In healthcare applications of WSN, the data loss due to congestion may cause death alarm for a patient in critical condition. Therefore, an efficient congestion avoidance or otherwise an efficient congestion control mechanism is required. In this paper, we present an energy efficient reliable multi-path data transmission protocol for reliable data transport over WSN for the health care application. The emergency data and sensitive data packets are transmitted through an alternate path having minimum correlation with transmission interference during congestion. The proposed protocol attempts to avoid congestion by computing the probability of congestion at the intermediate nodes and transmission rate at the intermediate node is adjusted. The buffer of each node is partitioned to support fair and efficient data delivery. The reliability of the proposed protocol is achieved through hop-by-hop loss recovery and acknowledgement. The performance of the proposed protocol is evaluated through extensive simulations. The simulation results reveal that it outperforms the existing congestion control protocols for healthcare application in terms of energy efficiency, reliability and end-to-end delivery ratio.