Volume Changes of Iron Oxide Compacts under Isothermal Reduction Conditions

Compacts made from chemically grade Fe₂O₃ were fired at 1473K for 6 hrs. The fired compacts were isothermally reduced either by hydrogen or carbon monoxide at 1073–1373K. The O₂ weight‐loss resulting from the reduction process was continuously recorded as a function of time using TGA technique, whereas the volume change at different reduction conditions was measured by displacement method. Porosity measurements, microscopic examination and X‐ray diffraction analysis were used to characterize the fired and reduced products. The rate of reduction at both the initial and final stages was increased with temperature. The reduction mechanism deduced from the correlations between apparent activation energy values, structure of partially reduced compacts and application of gas‐solid reaction models revealed the reduction rate (dr/dt) at both the initial and final stages. At early stages, the reduction was controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism, while at the final stages the interfacial chemical reaction was the rate determining step. In H₂ reduction, maximum swelling (80%) was obtained at 1373K, which was attributed to the formation of metallic iron plates. In CO reduction, catastrophic swelling (255%) was obtained at 1198K due to the formation of metallic iron plates and whiskers.     

Preparation and characterization of ZnSe nanoparticles by mechanochemical process

Nanocrystalline ZnSe powder was prepared by mechanochemical process from Zn and Se pure granules. Zn and Se granules transformed to powder during mechanochemical reaction and ZnSe phase was observed after milling time of 16 min by XRD measurements. The crystallite size was measured to be 9–10 nm, while the powder particle size was found to be in the range 90–500 nm in the milling time range 20–60 min as measured by size analyzer and SEM. The homogeneity of the powder was confirmed by EDX analysis. The optical band gap was estimated from optical absorbance curve and possess the value in the range 2.58–2.95 eV. The absorbance peak was observed to be wider according the wide distribution of the crystallite size which affect on the energy gap according to energy gap confinement.     

Flexural and Interfacial Behavior of FRP-Strengthened Reinforced Concrete Beams

Although there is a large amount of experimental data available on the fiber-reinforced polymer (FRP) strengthening of concrete structures, a full understanding of the various debonding phenomena is somewhat lacking. As a contribution to fill this need, two-dimensional and three-dimensional (3D) nonlinear displacement-controlled finite-element (FE) models are developed to investigate the flexural and FRP/concrete interfacial responses of FRP-strengthened reinforced concrete beams. Interface elements are used to simulate the FRP/concrete interfacial behavior before and after cracking. The analysis is carried out using two different relations for the interface; namely, nonlinear and bilinear bond–slip laws. The results predicted using these two laws are compared to those based on the full-bond assumption. The FE models are capable of simulating the various failure modes, including debonding of the FRP, either at the plate end or at intermediate cracks. The 3D model is created to accommodate cases of FRP-strengthened reinforced concrete beams utilizing FRP anchorage systems. In addition, the models successfully represent the actual interfacial behavior at the vicinities of cracks including the stress/slip concentrations and fluctuations. Results are presented in terms of the ultimate load carrying capacities, failure modes and deformational characteristics. Special emphasis is placed on the FRP/concrete interfacial behavior and cracking of the concrete. The numerical results are compared to available experimental data for 25 specimens categorized in six series, and they show a very good agreement.     

Successful Delivery of Public-Private Partnerships for Infrastructure Development

Two common approaches have been used by governments for the implementation of public-private partnerships (PPPs): a finance-based approach that aims to use private financing to satisfy infrastructure needs, and a service-based approach that aims to optimize the time and cost efficiencies in service delivery. The implementation of PPPs, however, may suffer from legal, political, and cultural impediments. In the United States, the federal government enabled a number of acts to ease the impediments and promote PPPs for infrastructure development. Based on a detailed analysis of PPPs in the United Kingdom and British Columbia, Canada, this paper describes principles that would characterize the implementation of PPPs at the program level (e.g., whether the implementation is successful). The principles pertain to the: availability of a PPP legal framework and implementation units; perception of the private finance objectives, risk allocation consequences, and value-for-money objectives; maintenance of PPPs process transparency; standardization of procedures; and use of performance specifications. Guidelines for successful implementation are explained and discussed in the context of the United States PPPs experience and impediments.     

VANET QoS-OLSR: QoS-based clustering protocol for Vehicular Ad hoc Networks

In this paper, we address the problem of clustering in Vehicular Ad hoc Networks (VANETs) using Quality of Service Optimized Link State Routing (QoS-OLSR) protocol. Several clustering algorithms have been proposed for VANET and MANET. However, the mobility-based algorithms ignore the Quality of Service requirements that are important for VANET safety, emergency, and multimedia services while the QoS-based algorithms ignore the high speed mobility constraints since they are dedicated for Mobile Ad hoc Networks (MANETs). Our solution is a new QoS-based clustering algorithm that considers a tradeoff between QoS requirements and high speed mobility constraints. The goal is to form stable clusters and maintain the stability during communications and link failures while satisfying the Quality of Service requirements. This is achieved by: (1) considering the high mobility metrics while computing the QoS, (2) using Ant Colony Optimization for MPRs selection, and (3) using MPR recovery algorithm able to select alternatives and keep the network connected in case of link failures. Performance analysis and simulation results show that the proposed model can maintain the network stability, reduce the end-to-end delay, increase the packet delivery ratio, and reduce the communications overhead.     

Electrocatalytic evolution of hydrogen on a novel SrPdO3 perovskite electrode

SrPdO₃ was prepared for the first time by the citrate method. XRD, SEM and TGA characterizations were carried out. The catalytic activity toward hydrogen evolution reaction (HER) was investigated, the activation energy, and reaction order and reaction mechanism have been determined using Tafel polarization and impedance techniques. The modified surface showed up to 100 times more efficiency towards electrocatalytic production of hydrogen. Adsorption of hydrogen on the catalyst was the rate-determining step and the reaction order at the surface of the catalyst is 0.86. The molar magnetic susceptibility was measured using Faraday's method and anti-ferromagnetic character was observed.     

New polymer synthesis. XXX. Synthesis and thermal behavior of new organometallic polyketones and copolyketones based on diferrocenylidenecycloheptanone

A new interesting category of organometallic polyketones and copolyketones was synthesized via Friedel–Crafts reactions through the polymerization of 2,7‐bis[(2‐ferrocenyl)methylene] cycloheptanone ( II ) with different diacid chlorides. The model compound was synthesized by reacting monomer II with benzoyl chloride and characterized by ¹H‐NMR, IR, and elemental analyses. The polyketones and copolyketones were insoluble in most organic solvents but easily soluble in concentrated H₂SO₄. The thermal properties of these polyketones and copolyketones were evaluated and correlated to their structural units by TGA and DTG measurements and had inherent viscosity of 0.32–0.65 dI g^?1. Moreover, the electrical conductivity of polyketone Va and copolyketone VI was investigated above the temperature range (300–500 K) and followed an Arrhenius equation with activation energy 2.09 eV. Also, the morphological properties of selected example of polyketones were detected by scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2394–2401, 2005     

Surface pressure and wind load characteristics on prisms immersed in a simulated transient gust front flow field

Thunderstorm generated gust fronts are responsible for various degrees of structural damage in many areas of the world. However, the resulting impact of gust front winds is not fully understood to such a level that their flow kinematics, dynamics and impact on structures can be quantified with some certainty. Gust front winds are transient in nature and have a flow profile which differs significantly from a typical boundary layer flow field. This study focuses on investigating the effects of this flow profile and its transient nature on the aerodynamics of bluff, prismatic bodies. A gust front type flow field is generated using a multiple fan wind tunnel and the resulting surface pressures are captured on a suite of prismatic models, which vary in size in relationship to the oncoming wind profile. The temporal variations in surface pressures are analyzed using traditional time, frequency and time-frequency domain schemes. Results indicate the changing nature of the surface pressure field in time, highlighting both qualitative and quantitative differences between local and area-averaged pressures under a host of flow profiles.     

Approach to performance optimisation in frequency-weighted memory network pattern classifiers

The performance of memory network pattern classifiers based on a feature frequency-weighting scheme can suffer from an inappropriate arbitrary choice of zero-frequency component in the computation of discriminant functions. This letter assesses the effect of optimising this factor, emphasising the value of optimisation in pairwise class discrimination, which is of particular relevance in the design of efficient hierarchical classifier architectures.     

Synthesis of a new sulphonated cation exchange resin and its application in catalysed hydrolysis of esters

Samples of an acidic cation exchanger have been prepared by sulphonation of acrylonitrile butadiene styrene copolymer previously cross-linked with phenol-formaldehyde resin. The samples having a cation exchange capacity of 3.48 meqg^–1, are being introduced as new catalysts in the hydrolysis of ethyl acetate. The synthesized cation exchanger shows good thermal and chemical stability. Hydrolysis rate constants (K _r values) for the catalysed reaction have been determined. The efficiency of the resin catalyst,q, is shown to be a function of resin concentration.