Reduced graphene oxide-supported Pd@Au bimetallic nano electrocatalyst for enhanced oxygen reduction reaction in alkaline media

Rational design and synthesis of core-shell bimetallic nanoparticles with tailored structural and functional properties is highly sought to realize clean and energy-efficient fuel cell systems. Herein, PdAu bimetallic nanoparticles (NPs) with core-shell morphology (Pd_Core–Au_Shell) were fabricated on the surface of reduced graphene oxide (RGO) support by a facile two-step protocol. In the first step, Pd_Core–Ag_Shell bimetallic NPs were synthesized on RGO support by reducing Pd²⁺and Ag⁺ ions with methyl ammonia borane (MeAB). Later, Pd_Core–Au_Shell bimetallic NPs were conveniently fabricated on RGO support via a galvanic replacement strategy involving sacrificial oxidation of metallic silver and reduction of gold ions. The resulting core/shell bimetallic NPs were characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray spectroscopy (EDS), Fourier-Transform Infrared Spectroscopy (FT-IR) and cyclic voltrammetry (CV). The electrocatalytic performance of core/shell nanostructures for the room temperature oxygen reduction reaction (ORR) in alkaline media were systematically performed by CV. The electrode-area-normalized ORR activity of RGO-supported Pd_Core–Au_Shell NPs was higher than the corresponding commercially available carbon-supported Pt nanoparticles (Pt/C) at ?0.8 V vs Ag/AgCl (satd. KCl) (6.24 vs 5.34 mA cm^?2, respectively). Further, methanol-tolerant ORR activities of as-synthesized catalysts were also studied. The Au-on-Pd/RGO bimetallic NPs presented enhanced ORR activity both in presence and in the absence of methanol in comparison with a commercial Pt/C catalyst and as-synthesized Pd/RGO and Au/RGO catalysts. The enhanced catalytic activities of core/shell structures might be resulted owing to the optimized core/shell structure comprising of a small Pd core and a thin Au shell and synergistic effects offered by Pd and Au. The present synthesis protocol demonstrated for two-layer structure can be extended to multi-layered structures with desired functions and activities.     

Structure–property relation in varieties of silk fibers

Crystallite shape ellipsoid in different varieties of silk fibers namely (i) Chinese (ii) Indian, and (iii) Japanese, has been computed using wide‐angle X‐ray data and Hosemann's one‐dimensional paracrystalline model. The estimated microcrystalline parameters are correlated with the observed physical property of the silk fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1979–1985, 2001     

Scintiphotography of lungs with dry aerosol--generation and delivery system: concise communication

A compressed-air nebulizer with low holdup and high output was used to nebulize [99mTc] pertechnetate presented in normal saline. Generated droplets were dried in line and led to an inhalation chamber from which the dry aerosol was inhaled using a nose or mouth inhalation unit. The mass median diameter of the particles was 0.8 microns, with an associated geometric standard deviation of 2.0. The deep lung delivery efficiency--defined as the ratio of the activity deposited in the lung area to the activity nebulized--was found to be reproducible and consistent (15-22%) in all the subjects studied. A 3-5 min inhalation of aerosol, nebulized from 20 mCi, was sufficient to provide a lung image of good information density. No noticeable deposit was seen in the trachea or major brochi. The system is inexpensive, stable in performance, adaptable to other solutions or colloids, and is promising for routine use.     

Design charts for optimal design of T-beam floors

Mathematical programming techniques have been used to minimize the cost of T-beam floors. One-way continous slabs and simply supported T-beams have been designed by the limit state approach in accordance with CP 110–1972 using M25 grade concrete and cold worked high yield reinforcement. Cost of one of the bays has been minimized using the DFP algorithm. Parametric studies have been carried out for various span ratios, cost ratios of materials and magnitudes of imposed loads. Use of the design charts developed has been explained.     

EOQ Formula under Varying Marketing Policies and Conditions

This note deals with a method of arriving at an EOQ formula taking into account the effect of varying marketing policies and conditions on the demand and the possibility of a random fraction of the ordered items getting damaged. Two special cases are considered wherein explicit expressions for the EOQ are given.     

Reliability modeling of on-surface transit systems with human errors

This paper presents two newly developed Markov models representing on-surface transportation systems subject to hardware failures and human errors. Transit system reliability, steady state availability, mean time to failure (MTTF) and variance of time to failure formulas are developed. Selective plots are shown for each model.     

The state of reliability design specifications in Canadian industries: A survey

This paper presents the findings of a recent survey conducted on ‘reliability design specifications in Canadian manufacturing and service industries’. The survey is based upon a questionnaire mailed to various manufacturing and service industries in Canada. The questionnaire covered different aspects of organizational structure, reasons for emphasis on reliability and maintainability, areas of reliability engineering requiring improvement, most important parameters in equipment reliability specification, measures to improve system/equipment reliability, use of international or U.S. Military standards (reliability) in design specifications, reliability techniques and parameters specified when procuring an item, etc. The respondent organizations are classified into several groups, namely, Aerospace and defence, Electronics, Mechanical, Transportation, and others. General (all combined) and groupwise response analyses are performed.     

High pressure and low temperature conducting properties of organic semiconducting metal-anthraquinones

High pressure and low temperature conducting properties of 1,4-diamino anthraquinone, with metals such as cobalt, nickel, copper, and silver, and reported. The complexes formed are oxidatively and thermally stable and are insoluble in common organic solvents. They possess interesting conducting properties. All are semiconductors, showing conductivity in the range 1.98 × 10^?1 to 1.36 × 10^?6 S/cm, depending upon the metal atom present in the complex. Low temperature (300 K to 30 K) and high pressure (up to 6 GPa) conductivity properties of these materials are reported. Copper complexes have been studied in detail, as they show interesting conducting properties. © 1993 John Wiley & Sons, Inc.     

A method to evaluate reliability of systems with critical and non-critical human errors

This paper presents a newly developed method to perform reliability analysis of redundant systems with critical and non-critical human errors. The method is demonstrated using k-out-of-n units, parallel and series-parallel configurations. Time dependent analyses are developed for exponentially and Rayleigh distributed failure times. System reliability and mean time to failure formulas are presented.