Boron nitride based polyaniline nanocomposite: Preparation,property, and application

In this study, we report first time the electrical properties and photocatalytic activity of HCl doped polyaniline (Pani) and Pani/boron nitride (Pani/BN) nanocomposite prepared by in situ polymerization of aniline using potassium persulfate (K₂S₂O₈) in the presence of hexagonal boron nitride (h‐BN). The prepared Pani and Pani/BN nanocomposite were characterized by Fourier transform infrared, X‐ray diffraction, Thermogravimetric analysis, Scanning electron microscope, and Transmission electron microscope. The stability of the Pani/BN nanocomposite in comparison of Pani in terms of the DC electrical conductivity retention was investigated under isothermal and cyclic aging conditions. The Pani/BN nanocomposite in terms of DC electrical conductivity was observed to be comparatively more thermally stable than Pani. The degradation of Methylene blue (MB) and Rhodamine B (RhB) under UV‐light irradiation were 50 and 56.4%, respectively, over Pani and 65.7 and 71.6%, respectively, over Pani/BN. The results indicated that the extent of degradation of MB and RhB was greater over nanocomposite material than Pani, which may result due to high electron–hole pairs charge separation under UV light. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43989.     

Throughput-efficient coalition formation of selfish/altruistic nodes in ad hoc networks: a hedonic game approach

In this paper, we analyze the problem of throughput-efficient distributed coalition formation (CF) of selfish/altruistic nodes in ad hoc radio networks. We formulate the problem as a hedonic CF game with non-transferable utility and propose different preference relations (CF rules) based on individual/group rate improvement of distributed nodes. We develop a hedonic CF algorithm, through which distributed nodes may self-organize into stable throughput-efficient disjoint coalitions. We apply the concept of frequency reuse over different coalitions, such that the members of each coalition will transmit over orthogonal sub-bands with the available spectrum being optimally allocated among them. We study the computational complexity and convergence properties of the proposed hedonic CF algorithm under selfish and altruistic preferences, and present means to guarantee Nash-stability. In addition, we identify the scenarios in which a CF process might lead to instability (CF cycle), and we propose methods to avoid cycles and define different exit procedures if a CF cycle is inevitable. Performance analysis shows that the proposed algorithm with optimal bandwidth allocation provides a substantial gain, in terms of average payoff per link, over existing coalition formation algorithms for a wide SNR range.     

Experimental and physical approaches on a novel semiconducting-ionic membrane fuel cell

Semiconducting-ionic membranes (SIMs) have exhibited significant superiority to replace the conventional ionic electrolytes in solid oxide fuel cells (SOFCs). One interesting phenomenon is that the SIMs can successfully avoid the underlying short-circuiting issue and power losses while bringing significantly enhanced power output. It is crucial to understand the physics in such devices as they show distinct electrochemical processes with conventional fuel cells. We first presented experimental studies of a SIM fuel cell based on a composite of semiconductor LiCo_0.8Fe_0.2O₂ (LCF) and ionic conductor Sm-doped CeO₂ (SDC), which achieved a remarkable power density of 1150 mW cm^?2 at 550 °C along with a high open circuit voltage (OCV) of 1.04 V. Then, for the first time we used a physical model via combining a semiconductor-ionic contact junction with a rectifying layer which blocks the electron leakage to describe such unique SIM device and excellent performance. Current and power are the most important characteristics for the device, by introducing the rectifying layer we described the SIM physical nature and new device process. This work presented a new view on advanced SIM SOFC science and technology from physics.     

Neural network optimized with evolutionary computing technique for solving the 2-dimensional Bratu problem

In this paper, a stochastic technique is developed to solve 2-dimensional Bratu equations using feed-forward artificial neural networks, optimized with genetic and interior-point algorithms. The 2-dimensional equations are first transformed into a 1-dimensional boundary value problem, and a mathematical model of the transformed equation is then formulated with neural networks using an unsupervised error. Network weights are optimized to minimize the error. Evolutionary computing based on genetic algorithms is used as a tool for global search, integrated with an interior-point method for rapid local convergence. The methodology is applied to solve three cases of boundary value problems for the Bratu equations. The accuracy, convergence and effectiveness of the scheme is validated for a large number of simulations. Comparison of results is made with the exact solution derived using MATHEMATICA, and is found to be in good agreement.     

Shape optimization of wire-wrapped fuel assembly using Kriging metamodeling technique

In this work, shape optimization of a wire-wrapped fuel assembly in a liquid metal reactor has been carried out by combining a three-dimensional Reynolds-averaged Navier–Stokes analysis with the Kriging method, a well-known metamodeling technique for optimization. Sequential quadratic programming (SQP) is used to search the optimal point from the constructed metamodel. Two geometric design variables are selected for the optimization and design space is sampled using Latin Hypercube Sampling (LHS). The optimization problem has been defined as a maximization of the objective function, which is as a linear combination of heat transfer and friction loss related terms with a weighing factor. The objective function value is more sensitive to the ratio of the wire spacer diameter to the fuel rod diameter than to the ratio of the wire wrap pitch to the fuel rod diameter. The optimal values of the design variables are obtained by varying the weighting factor.     

Maleated high oleic sunflower oil‐treated cellulose fiber‐based styrene butadiene rubber composites

Surface treatment of cellulose fibers was performed with maleated high oleic sunflower oil (MSOHO). The MSOHO‐treated cellulose fibers and unmodified cellulose fibers were dispersed in styrene butadiene rubber (SBR) using a two roll mill. Vapor grown carbon nanofibers (VGCNF) were also incorporated at only one parts per hundred rubber (phr) in unmodified cellulose fibers/SBR composites. The curing characteristics, mechanical properties, and water absorption of the resulting composites were determined. MSOHO‐treated fibers completed curing at much slower rate and also decreased the cure density of composites, compared to unmodified fibers. In contrast, the combination of VGCNF and unmodified cellulose fibers accelerated the SBR curing process, but reduced the cure density. MSOHO treatment improved the dispersion of the fibers in the SBR, which resulted in improved mechanical properties of composites. The composite incorporating 1 phr VGCNF and 15 phr unmodified cellulose fibers showed the greatest increase in tensile strength as compared with neat SBR. POLYM. COMPOS. 37:1113–1121, 2016. © 2014 Society of Plastics Engineers     

A medium access protocol exploiting multiuser-detection in CDMA ad-hoc networks

A new medium access protocol which exploits the physical layer capability of multiuser detection is proposed to help in improving the throughput/delay performance of ad-hoc networks. When more than one node has packets buffered for a common node in the neighborhood, all such nodes can simultaneously transmit their packets to the common receiver after reserving their surrounding channel. This is achieved in our protocol by extending the (sender-initiated) CSMA/CA collision avoidance framework by the receiver-initiated medium access technique and incorporating the transmission power control. We analyze the improvement in the throughput that can be achieved over the basic sender-initiated collision avoidance protocol in the network. Since the throughput improvement via multi-packet reception is influenced by the network layer activity as well, the performance of our protocol rolls back to that of the basic sender-initiated protocol in case of no coordination from the network layer. For the evaluation of performance of our protocol we simulate ad-hoc networks for different network topologies and traffic configurations. We observe the scheme to be capable in significantly improving the throughput/delay performance of the network.     

Effect of Cooling Rate on Microstructure and Mechanical Properties of Eutectoid Steel Under Cyclic Heat Treatment

A systematic study has been carried out to ascertain the effect of cooling rate on structure and mechanical properties of eutectoid steel subjected to a novel incomplete austenitization-based cyclic heat treatment process up to 4 cycles. Each cycle consists of a short-duration holding (6 min) at 775 °C (above A₁) followed by cooling at different rates (furnace cooling, forced air cooling and ice-brine quenching). Microstructure and properties are found to be strongly dependent on cooling rate. In pearlitic transformation regime, lamellar disintegration completes in 61 h and 48 min for cyclic furnace cooling. This leads to a spheroidized structure possessing a lower hardness and strength than that obtained in as-received annealed condition. On contrary, lamellar disintegration does not occur for cyclic forced air cooling with high air flow rate (78 m³ h^?1). Rather, a novel microstructure consisting of submicroscopic cementite particles in a ‘interweaved pearlite’ matrix is developed after 4 cycles. This provides an enhancement in hardness (395 HV), yield strength (473 MPa) and UTS (830 MPa) along with retention of a reasonable ductility (%Elongation = 19) as compared to as-received annealed condition (hardness = 222 HV, YS = 358 MPa, UTS = 740 MPa, %Elongation = 21).