Swage casting of A380 alloy

Swage casting is a new casting technique which combines the advantages of squeeze, centrifugal and semi-solid casting methods. In this new casting method, components with one rotating axis can be produced on a swage casting machine from molten metal in a one-step operation. A shape like a “bomb-body” is chosen to demonstrate the advantages of this new method by using A380 Al–Si–Cu alloy. The same alloy is also cast with centrifugal and squeeze casting methods. In this study, the swage casting method and its features are briefly described. The final microstructures, mechanical properties and amount of porosity of the cast pieces produced by squeeze, centrifugal and swage casting methods are compared. Swage cast pieces showed a different composition of microstructure that consists of fine dendritic particles at the chill ends and a mixture of spherical and rosette shaped particles at the core. The swage cast pieces also have a slightly higher mechanical strength as indicated by tensile strength and Brinell hardness values.     

Frequency independent‐dependent conductivity and dielectric properties of some ionomers

The preparation and physical properties of some ionomers have been investigated. The addition of CH₃I significantly improved the conductivity of the ionomers. At room temperature, the highest ionic conductivity value was found to be 4.93 10⁻⁸ S cm⁻¹ in the I4 ionomer. The conductivity data do not obey the Arrhenius law and the non‐linearity indicates ionic transport. The alternating current conductivity parameters and dielectric constants of the ionomers were determined. Copyright © 2005 Society of Chemical Industry     

Cell‐loss control in multiplexing of VBR video over ATM networks

In this article we investigate the impacts of interspacing and source polling policies on the cell‐loss rates in transmission of variable bit rate video sources over Asynchronous Transfer Mode networks. We present a mathematical model that finds the approximate optimal starting times of the video sources that minimize the congestion at the multiplexer. Combined with the approximate optimal source starting times, we propose a source ordering and polling policy for reducing the cell‐loss rates. The proposed policy is tested against alternative policies using simulation of pre‐recorded video data. This revised version was published online in June 2006 with corrections to the Cover Date.     

Experimental determination of the overall heat loss coefficient for energy requirement of greenhouse heating

This paper presents an experimental determination of energy requirement for greenhouse heating. The overall heat loss coefficient, heat input, the control factor for air‐tightness, the rate of heat loss and the thermal screen effectiveness were calculated. The relationships between the overall heat loss coefficient and the wind speed, and the outside temperature were modelled, including the measured and calculated values. It was found that the thermal screen effectiveness was 16 and 19.8% for the polyethylene (PE) and polyester screens, respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Static and dynamic bifurcations associated with a double-zero eigenvalue

This paper is concerned with the static and dynamic bifurcation phenomena exhibited by a nonlinear autonomous system in the vicinity of a double-zero eigenvalue. It is demonstrated analytically that such a coincident critical point is often located on the intersection of the divergence and flutter boundaries of the system. The analysis is performed via a new 'unification technique' which is based on an intrinsic perturbation procedure. The new approach is capable of yielding information about stability of solutions as well as incipient and secondary bifurcations. Indeed, the stability properties of the system and secondary Hopf bifurcations are discussed conveniently, and explicit results concerning post-critical solutions are presented. An illustrative example is analysed.     

Surface Characterization of Mild Steel During Atmospheric Corrosion After Being Treated by Sodium Dihydrogen Orthophosphate

Protection of Metals and Physical Chemistry of Surfaces - The objective of this study was to characterize the surfaces of the steel products produced locally during their exposure to the industrial...