The nature of silane at the interface of treated fillers

Silane coupling agents have been traditionally used to modify the surface properties of finely divided solids — ‘fillers’ such as powdered minerals and fibrous materials — in order to control their dispersion properties in various liquid media and resins. A number of techniques, including electrokinetic, contact angle, microscopic and the ‘desorption’ test, have been used to study the nature of filler surfaces treated with these agents.     

A Three-Phase Controlled-Current PWM Converter with Leading Power Factor

Experimental tests performed on a three-phase bipolartransistor controlled-current PWM power modulator show that it can operate with near-sinusoidal currents at 60 Hz with a 360-degree power angle range. Because of its capability to operate with leading power factor and good waveform, the PWM converter is a promising alternative to the thyristor Graetz bridge. A theoretical method based on the concept of ``local average' is presented.     

Growth of diamond thin films by chemical vapour deposition

Deposition of diamond thin films on non-diamond substrates at low pressures (<760 torr) and low temperatures (<2000°C) by chemical vapour deposition (CVD) has been the subject of intense research in the last few years. The structural and the electrical properties of CVD diamond films grown on p-type 〈111〉 and high-resistivity (>100 kΩ-cm) 〈100〉 oriented silicon substrates by hot filament chemical vapour deposition technique are described in this review paper.     

Synthesis of chemically coprecipitated hexagonal strontium-ferrite and its characterization

Highly uniform submicrometre size particles of hexagonal strontium ferrite (SrFe₁₂O₁₉) have been synthesized by chemical coprecipitation technique at pH ⋍ 13. Chemical coprecipitation technique has helped in bringing down the ferritization temperature from 1300 to 925° C which is revealed by DTA-TG and XRD studies. Reproducible uniform single domain particle size and its distribution has been observed by scanning electron microscopy. X-ray and Mossbauer studies have identified single phase ferrite with Fe³⁺ ions occupying the proper crystallographic sites. The performance parameters of the sintered isotropic strontium ferrite magnets have proved to be superior by about 20% over the ferrites prepared by conventional ceramic technique.     

Coupled multi‐scale cohesive modeling of failure in heterogeneous adhesives

A multi‐scale cohesive numerical framework is proposed to simulate the failure of heterogeneous adhesively bonded systems. This multi‐scale scheme is based on Hill's variational principle of energy equivalence between the higher and lower level scales. It provides an easy way to obtain accurate homogenized macroscopic properties while capturing the physics of failure processes at the micro‐scale in sufficient detail. We use an isotropic rate‐dependent damage model to mimic the failure response of the constituents of heterogeneous adhesives. The finite element method is used to solve the equilibrium equation at each scale. A nested iterative scheme inspired by the return mapping algorithm used in computational inelasticity is implemented. We propose a computationally attractive technique to couple the macro‐ and micro‐scales for rate‐dependent constitutive laws. We introduce an adhesive patch test to study the numerical performance, including spatial and temporal convergence of the multi‐scale scheme. We compare the solution of the multi‐scale cohesive scheme with a direct numerical simulation. Finally, we solve mode I and mode II fracture problems to demonstrate failure at the macro‐scale. Copyright © 2010 John Wiley & Sons, Ltd.     

Badumna: A decentralised network engine for virtual environments

Many of today’s virtual environment applications, such as massively multiplayer online games, involve a large and rapidly changing set of users. The server-based architecture of these applications makes its hard for them to support the dynamic user base and provide a scalable solution. Badumna, a scalable network engine for large-scale virtual environments, was developed to address these issues. The approach is based on a decentralised architecture using a structured peer-to-peer network. In order to ensure a highly scalable and efficient design, Badumna uses techniques that include neighbour introductions and the formation of dynamic bounded regions to reduce the load on the peer-to-peer network. The performance of Badumna is evaluated using extensive simulations. Results indicate that Badumna is able to scale to a large number of users without placing any additional overheads on the network that degrade performance.