Printable Fabrication of a Fully Integrated and Self‐Powered Sensor System on Plastic Substrates

Wearable and portable devices with desirable flexibility, operational safety, and long cruising time, are in urgent demand for applications in wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. Herein, a monolithically integrated self‐powered smart sensor system with printed interconnects, printed gas sensor for ethanol and acetone detection, and printable supercapacitors and embedded solar cells as energy sources, is successfully demonstrated in a wearable wristband fashion by utilizing inkjet printing as a proof‐of‐concept. In such a “wearable wristband”, the harvested solar energy can either directly drive the sensor and power up a light‐emitting diode as a warning signal, or can be stored in the supercapacitors in a standby mode, and the energy released from supercapacitors can compensate the intermittency of light illumination. To the best of our knowledge, the demonstration of such a self‐powered sensor system integrated onto a single piece of flexible substrate in a printable and additive manner has not previously been reported. Particularly, the printable supercapacitors deliver an areal capacitance of 12.9 mF cm^?2 and the printed SnO₂ gas sensor shows remarkable detection sensitivity under room temperature. The printable strategies for device fabrication and system integration developed here show great potency for scalable and facile fabrication of a variety of wearable devices.     

Pareto Optimal Multigene Genetic Programming for Prediction of Longitudinal Dispersion Coefficient

Water Resources Management - The longitudinal dispersion coefficient (Kx) is fundamental to modeling of pollutant and sediment transport in natural rivers, but a general expression for Kx, with...     

Comparative Study of Conventional and Computerized Reconstruction Techniques for Flow Time Series Data of Hydrometric Station

Water Resources Management - One of the undeniable requirements in hydrological forecasting and water resources studies is the availability of reliable information. Due to the various reasons, time...     

Emulating Software Defined Network using Mininet-ns3-WIFI Integration for Wireless Networks

SDN enables a new networking paradigm probable to improve system efficiency where complex networks are easily managed and controlled. SDN allows network virtualization and advance programmability for customizing the behaviour of networking devices with user defined features even at run time. SDN separates network control and data planes. Intelligently controlled network management and operation, such that routing is eliminated from forwarding elements (switches) while shifting the routing logic in a centralized module named SDN Controller. Mininet is Linux based network emulator which is cost effective for implementing SDN having in built support of OpenFlow switches. This paper presents practical implementation of Mininet with ns-3 using Wi-Fi. Previous results reported in literature were limited upto 512 nodes in Mininet. Tests are conducted in Mininet by varying number of nodes in two distinct scenarios based on scalability and resource capabilities of the host system. We presented a low cost and reliable method allowing scalability with authenticity of results in real time environment. Simulation results show a marked improvement in time required for creating a topology designed for 3 nodes with powerful resources i.e. only 0.077 sec and 4.512 sec with limited resources, however with 2047 nodes required time is 1623.547 sec for powerful resources and 4615.115 sec with less capable resources respectively.

     

Electromechanical properties of ternary BiFeO<Subscript>3</Subscript>−0.35BaTiO<Subscript>3</Subscript>–BiGaO<Subscript>3</Subscript> piezoelectric ceramics

In the present work, composition dependent crystal structure, ferroelectric, piezoelectric, and temperature dependent dielectric properties of the BiGaO₃-modified (1–x)(0.65Bi_1.05FeO₃–0.35BaTiO₃) (BFBT35–xBG, where x?=?0.00–0.03) lead-free ceramics were systematically investigated by solid-state reaction method, followed by water quenching process. The substitution of BG successfully diffuses into the lattice of the BFBT ceramics, without changing the pseudo-cubic structure of the samples. The scanning electron microscopy (SEM) results revealed that the average grain size was increased with BG-content in BFBT system. The BFBT–xBG ceramics showed a maximum in permittivity (?_max) at temperatures (T_max) above 500 °C in the compositional range of 0.00?≤?x?≤?0.03. The electro-strain is measured to be 0.125% (d^*₃₃ ~ 250 pm/V) under unipolar fields (5 kV/mm) for BFBT–0.01BG ceramics. The same composition (x?=?0.01), large static piezoelectric constant (d₃₃ ~ 165 pC/N) and electromechanical coupling factor (k_p ~ 25%) were obtained. The above investigated characterizations suggests that BFBT–BG material is favorable for piezoelectric and high temperature applications.     

Evolution of ferroelectric and piezoelectric response by heat treatment in pseudocubic BiFeO<Subscript>3</Subscript>–BaTiO<Subscript>3</Subscript> ceramics

Heat treatment of ceramics is an important process to tailor the fine electromechanical properties. To explore the criteria for optimized heat treatment in a perovskite structure of (1–x)Bi_1.05FeO₃–xBaTiO₃ (BF–BT100x) system, the structural phase relation, ferroelectric and piezoelectric response of BF–BT36 and BF–BT40 ceramics prepared by furnace cooling (FC) and quenching process were investigated. The X-ray diffraction examination showed single pseudocubic perovskite structure for all the ceramics. The homogenous microstructure was obtained for all ceramics with relatively large grain size in the furnace cooled samples. Well saturated ferroelectric hysteresis loops and enhanced piezoelectric constant (d₃₃?=?97 pC/N) were achieved by quenching process. Dielectric curve of BF–BT36 showed large dielectric constant at its Curie temperature, however, BF–BT40 showed diffused relaxor-like dielectric anomalies. Quenched BF–BT36 samples showed typical butterfly like field induced strain curves, however negative strain decreased in BF–BT40 ceramics. From these investigated study, it is observed that BF–BT ceramics are very sensitive to the heat treatment process (furnace cooling and quenching) on the dielectric, electromechanical properties.     

Capacity and Channel Coding for Wireless Point-to-Point <Emphasis Type="Italic">Z</Emphasis><Superscript>2</Superscript> Channel

In this paper, we derive the capacity of the asymmetric \({\text{Z}}^{2}\)-channel, which has been presented for the first time as an optimization problem. Similar to the Z-Channel, the proposed \({\text{Z}}^{2}\)-channel can be modelled as a practical interference wireless channel. In addition, the capacity behavior of \({\text{Z}}^{2}\)-channel is discussed and some examples and simulation results for the capacity is presented. Also a code plan has been applied for \({\text{Z}}^{2}\)-channel, based on repetition code to simulate its performance and compare it with the original Z-channel. In conclusion, simulation results show that the \({\text{Z}}^{2}\)-channel can be used widely for different operating points.     

Facile synthesis of extremely biocompatible double‐network hydrogels based on chitosan and poly(vinyl alcohol) with enhanced mechanical properties

An easy and ecofriendly method for designing double‐network (DN) hydrogels based on chitosan and poly(vinyl alcohol) (PVA) with high mechanical performance is described. When covalent bonds in the networks are used as crosslinking agents in the achievement of a higher mechanical strength, the irreversible deformation of these hydrogels after a large force is applied is still one of the most important obstacles. To overcome this problem, we used physical crosslinking for both networks. The mechanical strength, surface morphology, and cytotoxicity of the films were studied by tensile testing, scanning electron microscopy analysis, and an MTT assay. The synthesized chitosan–PVA DN hydrogels showed a large improvement in the tensile strength to 11.52 MPa with an elongation of 265.6%. The surface morphologies of the films demonstrated the effective interactions between the two networks and a suitable porosity. Also, because of the use of a natural polymer and honey as a plasticizer, the cell culture indicated that the synthesized DN hydrogels had good biocompatibility (with 327.49 ± 11.22% viability) and could be used as capable biomaterials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45752.     

Conductive poly(vinylidene fluoride)/polyethylene/graphene blend‐nanocomposites: Relationship between rheology,morphology, and electrical conductivity

Relationship between rheology, morphology, and electrical conductivity of the poly(vinylidene fluoride)/polyethylene/graphene nano‐platelets ternary system (PVDF/PE/GnP) were investigated. All the blend nanocomposites were prepared via a two‐step melt mixing method. GnP (0.75 and 1.5 wt %) was first compounded with PVDF and then the resulted premixtuers were melt mixed with PE to achieve the desired compositions. The corresponding reference nanocomposites and filler‐less blends were also prepared. Effect of an interfacial agent (PEMA; maleic anhydride grafted polyethylene) was also studied in this work. The results of rheological analysis in conjunction with the Raman spectroscopy experiments revealed that GnP had higher affinity to PVDF than PE, which in turn led to creation of conductive networks of GnP (1.5 wt %) in PVDF matrix exhibiting the electrical conductivity of about 10^?2 (S/cm). Double percolated micro‐structure was predicted for the PE/PVDF 40/60 (wt/wt) blend containing low GnP content (0.9 wt %) and confirmed via direct electron microscopy and conductivity analysis. Using 5 wt % of the PEMA reduced the conductivity to 10^?5 (S/cm) and further increase in PEMA content to 10 wt % led to non‐conductive characteristics. The latter was attributed to the migration of GnP from the PVDF phase to PE/PEMA phase and hence disturbance of double percolated micro‐structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46333.