Genetic programming-assisted multi-scale optimization for multi-objective dynamic performance of laminated composites: the advantage of more elementary-level analyses

Neural Computing and Applications - High-fidelity multi-scale design optimization of many real-life applications in structural engineering still remains largely intractable due to the...     

XMSN: An efficient cross‐layer protocol for mixed wireless sensor networks

The application of wireless sensor networks (WSNs) technology in monitoring systems is demanding more efficient services to fulfill the requirements of the monitoring task. For this purpose, the simultaneous presence of features such as different communication mediums (air and water) used by nodes and various sizes of data generated by heterogeneous nodes are the key obstacles to build a communication protocol, which can ensure the reliable data delivery. This work terms such WSNs as mixed wireless sensor networks (MWSNs) which contains the aforementioned features. In this paper, we introduce a new cross‐layer protocol for mixed wireless sensor network (XMSN) which can adapt these features. The proposed cross layer protocol XMSN for such mixed environment is implemented and analyzed extensively in Castalia simulator. The performance of XMSN is compared with composition of well‐known protocols, namely, CTP plus BoX‐MAC‐2. The result shows that XMSN has better efficiency in terms of end‐to‐end delay, energy consumption, and goodput than that of CTP plus BoX‐MAC‐2 protocol.     

SAS-SIP: A secure authentication scheme based on ECC and a fuzzy extractor for session initiation protocol

The session initiation protocol is used for communication purposes in a client-server environment, where for each time session the client and server agree upon a shared secret session key through an authentication system. After establishing the connection between client and server for a session, both the parties use a session key to encrypt/decrypt messages for communicating within that session securely. Therefore, authentication plays a vital role in sharing the secret session key. Recently, Chaudhry et al. proposed an authentication scheme; yet this paper shows that Chaudhry et al.’s scheme has inefficient login and password change phases, respectively, and does not take care of the users’ anonymity. Therefore, this study proposes an enhanced scheme, referred to as the secure authentication scheme for session initiation protocol (SAS-SIP) to eliminate the drawbacks of the scheme proposed by Chaudhry et al. In addition, the proposed SAS-SIP uses fuzzy extractors to incorporate biometric data along with the password to enhance the degree of security in the authentication system. After performing the security analysis through a random oracle model, this paper concludes that SAS-SIP is secure from secret information retrieval of communicators to the attacker. Furthermore, it has a better trade-off among several measurement costs along with security.     

Physical,mechanical, and morphological behavior of sequential polybutadiene–poly(methyl methacrylate) interpenetrating polymer networks

Both full and semi-interpenetrating polymer networks (IPNs) of polybutadiene and poly(methyl methacrylate) were synthesized by sequential polymerization. The effect of compositional variation and the cross-linking agent of both elastomer and plastomer on the physical, mechanical, and morphological properties were investigated. Full-IPNs exhibited improved tensile strength, modulus, tear strength, gel content, and density, whereas the corresponding semi-IPNs exhibited better toughness and elongation at break. Phase morphology of full-IPNs were characterized by compact, tight network structures compared to those of semi-IPNs. © 1994 John Wiley & Sons, Inc.     

Compositional modification of Sr2TiCoO6 double perovskites by Mo and La for high temperature thermoelectric applications

Double perovskites (A₂B^/B^//O₆) are an interesting family of materials, which are amenable to compositional modification. Recently double perovskites have shown promising thermoelectric properties especially at high temperature. In this report, we investigated the combination of two different cubic double perovskites with similar lattice constant but one (Sr₂TiCoO₆) showing good Seebeck coefficient and the other (Sr₂TiMoO₆) with high electrical conductivity. Dense ceramic samples of Sr₂TiCo_0.5Mo_0.5O₆ and La_0.2Sr_1.8TiCo_0.5Mo_0.5O₆ were synthesized by solid state reaction method. Rietveld refinement of XRD data confirmed the cubic structure with Pm$\overline{3}$m space group in these ceramics. Doping of Mo in Sr₂TiCoO₆ helped in increasing its conductivity; however Seebeck coefficient showed the n-type behavior unlike the p-type conductivity observed in Sr₂TiCoO₆ ceramics. Aliovalent doping of La in Sr₂TiCo_0.5Mo_0.5O₆ further increased its conductivity and Seebeck coefficient demonstrated temperature driven p-type to n-type conduction switching behavior. Conductivity mechanism of these ceramics was found to be governed by small polaron hopping model. Temperature driven p-n switching observed in the thermopower (S) measurement of La_0.2Sr_1.8TiCo_0.5Mo_0.5O₆ was further explained by an analytical model.     

Multiple convection‐driven Falkner‐Skan flow of Carreau nanofluid along a permeable wedge: An analytical approach

The impression of multiple convective conditions on Falkner‐Skan flow along a permeable static/moving wedge is demonstrated here. The Carreau nanofluid model depending on the power law index is incorporated with the effects of thermophoresis and Brownian motion. A suitable similarity conversion is consumed to bring out the nonlinear ordinary differential equations (ODEs) from the partial differential system. The transformed system is tackled via analytical and numerical procedure by homotopy perturbation method and RK‐5 with shooting technique, respectively. Numerical computations assert that the growth of concentration and temperature boundary layer widths are in an inversely proportional relation to the permeability of the medium, whereas reverse effect is observed for conduction convection and conduction diffusion parameters. Also, with the enhancement of Brownian motion parameter, the rate of heat transport gets reduced for static wedge by 14.25% whereas for moving wedge the reduction is 10.61%. Another significant observation shows that the growth in mass transport with conduction diffusion is 17.65% greater for moving wedge in contrast to static one in accordance with other governing parameters.     

Performance improvement of DC-DC converter using L-D-based modified GaN-FET driver

Bootstrap capacitor in FET gate driver plays an important role in the transient performance of the half bridge configured synchronous buck DC-DC converter especially in the top switch. In this paper, a new bootstrap capacitor based GaN-FET driver is proposed. This new GaN-FET driver is tested in a synchronous buck converter for performance verification like immunity, transient response, and voltage ringing. A comparison study with the existing LM5113 (Texas Instrument)–based driver for GaN-FET and IR2110-based Si-MOSFET driver on a DC-DC converter is carried out to show the performance improvement using the proposed GaN-FET driver. The simulation study is performed on spice-based NI-Multisim 14.1. Finally, the designed GaN-FET driver is tested on a 60-W synchronous buck DC-DC converter in open-loop and closed-loop configuration.     

Enhanced Thermoelectric Performance of Rare-Earth-Free n-Type Oxide Perovskite Composite with Graphene Analogous 2D MXene

Here, the first experimental demonstration on the effect of incorporating new generation 2D material, MXene, on the thermoelectric performance of rare-earth-free oxide perovskite is reported. The charge localization phenomenon is predominant in the electron transport of doped SrTiO₃ perovskites, which deters from achieving a higher thermoelectric power factor in these oxides. In this work, it is shown that incorporating Ti₃C₂T_x MXene in a matrix of SrTi_0.85Nb_0.15O₃ (STN) facilitates the delocalization of electrons resulting in better than single-crystal-like electron mobility in polycrystalline composites. A 1851% increase in electrical conductivity and a 1000% enhancement in power factor are attained. Besides, anharmonicity caused by MXene in the STN matrix has led to enhanced Umklapp scattering giving rise to lower lattice thermal conductivity. Hence, 700% ZT enhancement is achieved in this composite. Further, a prototype of thermoelectric generator (TEG) using only n-type STN + MXene is fabricated and a power output of 38 mW is obtained, which is higher than the reported values for oxide TEG.     

Nanocomposites based on polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene and exfoliated graphite nanoplates: Effect of nanoplatelet loading on morphology and mechanical properties

Exfoliated graphite nanoplates (xGnPs)/polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene (SEBS) nanocomposites have been prepared by the simple melt-compounding approach. The structural, mechanical and viscoelastic properties of these composites were studied and compared. Wide-angle X-ray diffraction (WAXD) studies indicated that the processing of nanocomposites did not change the original d-spacing of xGnPs. Scanning electron microscopy observation on the fracture surfaces of the composites shows a uniform dispersion of xGnPs throughout SEBS matrix and strong interfacial adhesion between oxidized xGnPs and the matrix, which are responsible for the considerable enhancement of mechanical properties of the composites. It is found that the addition of xGnPs particles improved both the elastic modulus and storage modulus of pure SEBS significantly and the higher the xGnPs content, the higher the modulus of the nanocomposite. Moreover, the effects of dispersed xGnPs on the microphase separation of SEBS have also been investigated using small angle X-ray scattering (SAXS).     

Sleeping beauties in Computer Science: characterization and early identification

Scientometrics - While a large majority of scientific publications get most of their citations within the initial few years after publication, there is an interesting number of papers—termed...