Synthesis and dielectric properties of MXTi<Subscript>7</Subscript>O<Subscript>16</Subscript> (M = Ba and Sr; X = Mg and Zn) hollandite ceramics

MXTi₇O₁₆ (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (ε_r), loss tangent (tan δ) and temperature variation of dielectric constant (τ_εr) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.     

NoC synthesis flow for customized domain specific multiprocessor systems-on-chip

The growing complexity of customizable single-chip multiprocessors is requiring communication resources that can only be provided by a highly-scalable communication infrastructure. This trend is exemplified by the growing number of network-on-chip (NoC) architectures that have been proposed recently for system-on-chip (SoC) integration. Developing NoC-based systems tailored to a particular application domain is crucial for achieving high-performance, energy-efficient customized solutions. The effectiveness of this approach largely depends on the availability of an ad hoc design methodology that, starting from a high-level application specification, derives an optimized NoC configuration with respect to different design objectives and instantiates the selected application specific on-chip micronetwork. Automatic execution of these design steps is highly desirable to increase SoC design productivity. This work illustrates a complete synthesis flow, called Netchip, for customized NoC architectures, that partitions the development work into major steps (topology mapping, selection, and generation) and provides proper tools for their automatic execution (SUNMAP, xpipescompiler). The entire flow leverages the flexibility of a fully reusable and scalable network components library called xpipes, consisting of highly-parameterizable network building blocks (network interface, switches, switch-to-switch links) that are design-time tunable and composable to achieve arbitrary topologies and customized domain-specific NoC architectures. Several experimental case studies are presented In the work, showing the powerful design space exploration capabilities of the proposed methodology and tools.     

Non-linear viscoelastic model based ranking of modified binders for their rutting performance

Rutting is one of the most common distresses observed in bituminous pavements. A number of test procedures, associated parameters, and correlations have been developed for the binder and the mixture to evaluate their rutting performance. In this investigation, the rutting performance of an unmodified, and three modified binders (Elastomer, Plastomer and Crumb rubber) was evaluated separately for the binders and mixtures. Creep-recovery and stress relaxation experiments were carried out on binders in the temperature range of 46–70 \({^{\circ }}\)C. The mixtures were subjected to dry rut wheel testing at 50 and 60 \({^{\circ }}\)C. A nonlinear viscoelastic fluid model was used to capture the response of the binder. Using the material parameters identified separately for creep-recovery and stress relaxation experiments, the apparent viscosity was computed for each binder at different stress levels. It was seen that the ranking of mixtures evaluated from rut wheel testing was captured by the apparent viscosity predicted using the non-linear viscoelastic model.     

Efficacy of Novel Electroless Plating Process for Dense Pd/Cr2O3/PSS Membrane Fabrication

This work addresses the role of chromia diffusion barrier on the combinatorial plating characteristics of Pd plating baths during fabrication of dense Pd/Cr₂O₃/porous stainless steel (PSS) composite membranes and is compared with those obtained during fabrication of Pd/PSS membranes. Cr₂O₃ was deposited by electroplating technique followed with oxidation at 700°C and Pd films were deposited using a novel Pd electroless plating process that provides optimal performance. Apart from providing similar process characteristics, the Pd/Cr₂O₃/PSS membrane provided 15.2% lower Pd film thickness in comparison with Pd/PSS membrane for similar pore densification values.     

BER performance analysis of compound chaotic sequence (CCS)-based NR-DCSK system under multipath fading channel

This paper presents the performance analysis of compound chaotic sequence (CCS)-based noise reduction differential chaos shift keying (NR-DCSK) system under multipath Rayleigh fading channel conditions. The special characteristics of chaotic sequences are their deterministic randomness behaviour that adds security and multipath immunity to the data when used as a carrier in communication systems. In this paper, the chaotic sequences are generated by combining the outputs of chaotic maps, such as logistic map, Chebyshev map, Bernoulli shift map, tent map, etc., leading to new complex sequences known as CCSs. This sequence possesses more randomness, overcomes severe interference levels encountered during transmission and provides higher multipath immunity compared with those of pseudo-noise (PN) codes. Since NR-DCSK is a spread spectrum technique, its performance in wireless multipath fading channels has important considerations. The CCS is used as a carrier in NR-DCSK systems, which leads to improved bit error rate (BER) performance. Comparisons of simulation results to theoretical BER expressions of additive white Gaussian noise (AWGN) and Rayleigh fading channels have been carried out to test the efficiency of the proposed CCS-based NR-DCSK system.     

Fabrication, characterization, and enzymatic activity of fungal protease--nanogold membrane bioconjugate

This study describes the synthesis of a free-standing nanogold membrane by the spontaneous reduction of aqueous chloroaurate ions by the diamine molecule DAEE at a liquid-liquid interface. The free standing nanogold membrane, provides a biocompatible surface for the immobilization of proteins. F-Protease (F-Prot) was then bound to the nanogold membrane via interaction with the gold nanoparticles leading to a new class of biocatalyst. A highlight of the new biocatalyst wherein the enzyme is bound to the nanogold membrane is the ease with which separation from the reaction medium may be achieved by simple filtration. In relation to the free enzyme in solution, the F-Prot in the bioconjugate material exhibited a slightly higher biocatalytic activity and significantly enhanced pH and temperature stability. The F-Prot nanogold membrane bioconjugate material also exhibited excellent biocatalytic activity over ten successive reuse cycles.     

Spider silk as an active scaffold in the assembly of gold nanoparticles and application of the gold-silk bioconjugate in vapor sensing

Spider silk is being viewed with interest by materials scientists due to its excellent resilience and mechanical properties. In this paper we show that spider silk is an excellent scaffold for the one-step synthesis and assembly of gold nanoparticles. Formation of a gold nanoparticle-spider-silk bioconjugate material is accomplished by simple reaction of the fibers with aqueous chloroauric acid. The gold nanoparticles thus formed are strongly bound to the spider-silk fiber surface enabling study of the electrical properties of the nanobioconjugate. Using the well-known contraction/expansion behavior of the fibers in solvents of varying polarity, we show that exposure of the gold nanoparticle-spider silk bioconjugate to vapors of methanol and chloroform leads to changes in electrical transport through the nanoparticles and thus, the possibility of developing a vapor sensor. The bioconjugate shows excellent response time and cycling efficiency to methanol vapors. The activation energy of electron transport from one gold nanoparticle to another in the nanobiocojugate was determined from temperature-dependent electron-transport measurements to be approximately 1.7 eV.     

Placement of a manipulator for minimum cycle time

Productivity of a manipulator depends, largely, on the time it takes to traverse a path, which is a function of the capacity of the actuators to produce torque. Increasing the torque capacity of the actuators to reduce path traversal time may be unrealistic in many cases. Therefore, this article studies the effects of the manipulator location, within a workcell, on the path traversal time. The article defines the boundaries of the manipulator base locus when the end‐effector path is prescribed. Effects of joint mechanical limits and obstacles on this locus are also considered. The proposed algorithm uses nonlinear programming to search the manipulator base locus for the base location that yields the minimum time to traverse a path, subject to the actuator torque constraints of the manipulator. Detailed examples are included. ©1999 John Wiley & Sons, Inc.     

Effect of some VA group modifiers on R2O3 (R = Sb,Bi)–ZnF2–GeO2 glasses doped with CuO by means of spectroscopic and dielectric investigations

Transparent glasses 40Sb₂O₃–20ZnF₂–(40 − x)GeO₂:xCuO, and 40Bi₂O₃–20ZnF₂–(40 − y)GeO₂:yCuO with x = 0, 0.6 and 0 ≤ y ≤ 1 wt% were prepared by melt quenching technique and were characterized by XRD and differential thermal analysis. Spectroscopic studies like optical absorption, FTIR, Raman, EPR and dielectric parameters (such as ?′, loss(tan δ), and σ_ac) were carried out to examine the modifier and dopant effect on zinc germanate glass network. Optical absorption and EPR data have revealed that the environment of Cu²⁺ ions is more ionic in bismuth series rather than antimony glasses. Reduced bismuth ions have been found in pure and at lower concentration of dopant in Bi₂O₃ mixed glasses, which are useful for IR amplifications. FTIR and Raman spectra have indicated the conversion of GeO₄ to GeO₆ structural units by forming cross linking bonds like Bi–O–Ge, Ge–O–Cu, etc., and open the glass network with integration of Bi₂O₃ and CuO doping. It is also confirmed by decreasing T_g and E_g values. The temperature dependence of dielectric parameters at different frequencies was interpreted in terms of structural changes in the glass network.     

Optimization of the conductivity and yield of chemically synthesized polyaniline using a design of experiments

The electrical conductivity and yield of polyaniline (PANi) were optimized using a design of experiments (DOE). PANi samples were synthesized by the chemical oxidative polymerization of aniline using methane sulfonic acid as the dopant acid and ammonium persulfate as the oxidant. The main factors in the synthesis of PANi that can affect the conductivity were identified as (i) the concentration of dopant acid, (ii) oxidant‐to‐monomer ratio, and (iii) the addition rate of oxidant to monomer. Using a Box‐Behnken DOE method the regression equation, main effects plots, contour plots, and optimization plots for conductivity and yield were generated and analyzed. Under the optimized conditions of dopant acid concentration of 0.9M, an oxidant addition rate of 30 mL/h and an OM ratio of 0.9, PANi with a conductivity of 1.95 S/cm and yield of 95% was obtained. The observed trends in the four‐point probe conductivity measurements were correlated with the polymer structure using fourier transform infrared spectroscopy, X‐ray diffraction studies, and scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1047‐1057, 2013