Security and key management in IoT‐based wireless sensor networks: An authentication protocol using symmetric key

Wireless sensor networks (WSN) consist of hundreds of miniature sensor nodes to sense various events in the surrounding environment and report back to the base station. Sensor networks are at the base of internet of things (IoT) and smart computing applications where a function is performed as a result of sensed event or information. However, in resource‐limited WSN authenticating a remote user is a vital security concern. Recently, researchers put forth various authentication protocols to address different security issues. Gope et al presented a protocol claiming resistance against known attacks. A thorough analysis of their protocol shows that it is vulnerable to user traceability, stolen verifier, and denial of service (DoS) attacks. In this article, an enhanced symmetric key‐based authentication protocol for IoT‐based WSN has been presented. The proposed protocol has the ability to counter user traceability, stolen verifier, and DoS attacks. Furthermore, the proposed protocol has been simulated and verified using Proverif and BAN logic. The proposed protocol has the same communication cost as the baseline protocol; however, in computation cost, it has 52.63% efficiency as compared with the baseline protocol.     

Feasibility and performance evaluation of a 6LoWPAN‐enabled platform for ubiquitous healthcare monitoring

Technology has revolutionized medical practices by enabling more convenient and non‐intrusive monitoring of patient's health, leading to next generation ubiquitous healthcare (u‐healthcare). The exploitation of the Internet protocol version 6 addressing space along with the miniaturization of electronic devices has fostered providing interoperability and connectivity of wearable sensor devices in wireless body area networks to the Internet of Things. In this paper, we propose to integrate the IPv6 over low power wireless personal area network (6LoWPAN) to the u‐healthcare monitoring system architecture. The main objective is to study the feasibility of the 6LoWPAN‐enabled platform in real‐world scenarios dealing with medical data. The performance evaluation of this platform is carried out initially through simulations using OMNet++ and then supported by an experimental study using sensor motes and a customized micro‐computing unit. Performance metrics such as throughput, end‐to‐end delay, packet error rate, and energy consumption are investigated under acute health conditions, where patient's health information has to be sent continuously and at maximum rate to the care provider. The obtained results show that the proposed 6LoWPAN solution fulfills the main quality of service requirements of u‐healthcare applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Deterministic Polymorphic Engineering of MoTe2 for Photonic and Optoelectronic Applications

Developing selective and coherent polymorphic crystals at the nanoscale offers a novel strategy for designing integrated architectures for photonic and optoelectronic applications such as metasurfaces, optical gratings, photodetectors, and image sensors. Here, a direct optical writing approach is demonstrated to deterministically create polymorphic 2D materials by locally inducing metallic 1T′-MoTe₂ on the semiconducting 2H-MoTe₂ host layer. In the polymorphic-engineered MoTe₂, 2H- and 1T′- crystalline phases exhibit strong optical contrast from near-infrared to telecom-band ranges (1–1.5 µm), due to the change in the band structure and increase in surface roughness. Sevenfold enhancement of third harmonic generation intensity is realized with conversion efficiency (susceptibility) of ≈1.7 × 10⁻⁷ (1.1 × 10⁻¹⁹ m² V⁻²) and ≈1.7 × 10⁻⁸ (0.3 × 10⁻¹⁹ m² V⁻²) for 1T′ and 2H-MoTe₂, respectively at telecom-band ultrafast pump laser. Lastly, based on polymorphic engineering on MoTe₂, a Schottky photodiode with a high photoresponsivity of 90 AW⁻¹ is demonstrated. This study proposes facile polymorphic engineered structures that will greatly benefit realizing integrated photonics and optoelectronic circuits.     

Topological evolution of laminar juncture flows under different critical parameters

Horseshoe vortex topological structure has been studied extensively in the past, traditional “saddle of separation” and new “attachment saddle point” topologies found in literature both have theoretical basis and experimental and computational evidences for support. The laminar incompressible juncture flows at low Reynolds numbers especially are observed to have new topology. Studies concerning the existence of the new topology though found in literature, the topological evolution and its dependency on various critical flow parameters require further investigation. A Particle Image Velocimetry based analysis is carried out to observe the effect of aspect ratio, δ*/D and shape of the obstacle on laminar horseshoe vortex topology for small obstacles. Rise in aspect ratio evolves the topology from the traditional to new for all the cases observed. The circular cross section obstacles are found more apt to having the new topology compared to square cross sections. It is noted that the sweeping effect of the fluid above the vortex system in which horseshoe vortex is immersed plays a critical role in this evolution. Topological evolution is observed not only in the most upstream singular point region of horseshoe vortex system but also in the corner region. The corner vortex topology evolves from the traditional type to new one before the topological evolution of the most upstream singular point, resulting in a new topological pattern of the laminar juncture flows “separation-attachment combination”. The study may help extend the understanding of the three-dimensional boundary layer separation phenomenon.     

Progress on Epoxy/Polyamide and Inorganic Nanofiller-Based Hybrids: Introduction,Application, and Future Potential

An efficient method to obtain better properties of epoxy-based nanocomposites is to introduce thermoplastic polymer such as polyamide into thermosetting resin. Combined effect of both polymers provides extra-bonding sites for nanofiller dispersion. This review mainly covers inorganic nanofiller dispersed epoxy/polyamide nanocomposite and their applications. To understand interaction between thermoset epoxy and thermoplastic polyamide, knowledge of structure, synthesis, and categorization is worth important. Addition of inorganic nanofiller such as layered silicate and metal oxide results in enhanced thermomechanical, physiochemical, and anticorrosive properties of resultant nanocomposite. These nanocomposites have applications as protective coatings, adhesives, insulators in electrical devices, and in aerospace industries.     

Solvent‐stable UV‐cured acrylic polysulfone membranes

A systematic investigation of the effect of the presence of acrylate resin on polysulfone‐based membranes was performed with the aim of obtaining chemically stable crosslinked membranes without affecting their flux performances. The membranes were prepared via UV curing of the polymer dope followed by a non‐solvent‐induced phase separation process. Two different acrylic monomers were investigated and their amount was varied in the polymer dope, to study the influence of concentration on final results. High crosslinking degrees were achieved by irradiating the solution for one minute. Morphological investigations of the active surface and of the cross‐sections of the fabricated membranes showed that the typical porosity of ultrafiltration membranes was obtained starting from solutions containing a low amount of crosslinker (10 wt%), which is consistent with the water flux values which were comparable to that of the pristine polysulfone membrane. High concentrations of crosslinker resin in the initial polymer dope produced denser membranes with lower permeability. High rejection of 27 nm particles (>90%) was measured for all samples having measurable flux. The addition of the crosslinker allowed one to obtain stability in various solvents without affecting the flux and rejection performance of the porous membranes. © 2016 Society of Chemical Industry     

Reinforcement of electroactive characteristics in polyvinylidene fluoride electrospun nanofibers by intercalation of multi-walled carbon nanotubes

This research work reports on development and characterization of multi-walled carbon nanotube (MWCNT)-doped polyvinylidene difluoride (PVDF) nanofibers by the electrospinning method. PVDF is an extensively studied polymer both theoretically and experimentally due to its appealing ferroelectric, piezoelectric, and pyroelectric properties which strongly favors its promising applications in the development of micro/nanostructure devices. The foremost reason for its ferroelectric and piezoelectric behaviors has been attributed to its crystalline structure, specifically the presence of β-phase; however, the existence of the small percentage of β-phase in pristine PVDF limits its applications. To enhance the electroactive features in the PVDF, MWCNTs have been doped in it to prepare electrospun nanofibers, as electrospinning is a single-step approach. These nonwoven nanofibers were prepared at a DC voltage of 20 kV which were subsequently calcined at 100 °C for 12 h. The estimation of crystal structure and phase identification in these nanofibers have been determined by attenuated FT-IR and XRD, while the morphology, microstructure, mean diameter, and length have been examined by FE-SEM. The observed electrical conductivity, capacitance, permittivity (ε), conductivity (δ), and impedance (Z) in these samples have been tailored by doping a range of MWCNT contents and optimizing the experimental conditions.     

Enviro-Friendly Synthesis of Silver Nanoparticles Using Berberis lycium Leaf Extract and Their Antibacterial Efficacy

In the present study,an enviro-friendly synthesis of silver nanoparticles from Berberis lycium Royle leaf extract and their antibacterial efficacy against five pathogenic bacteria were investigated.This biosynthesis technique is proved to be advantageous over physical and chemical methods as no toxic chemicals are used.The structural and morphological characterization was made by UV-visible spectroscopy,scanning electron microscopy,and transmission electron microscopy.The synthesized nanoparticles were oval,rectangular,and spherical in shape,size ranges from 8 to 100 nm and exhibited an absorption peak at 458 nm.The biosynthesized silver nanoparticles have shown good antibacterial effect toward tested bacteria.It is believed that these biosynthesized silver nanoparticles can play a vital role in nano-based products in future.