On Multicast Routing for Wavelength-Routed WDM Networks with Dynamic Membership

Future broadband networks must support integrated services and offer flexible bandwidth usage. In our previous work in [1], we explored the optical link control (OLC) layer on the top of optical layer that enables the possibility of bandwidth on-demand (BoD) service directly over wavelength division multiplexed (WDM) networks. Today, more and more applications and services such as video-conferencing software and Virtual LAN service require multicast support over the underlying networks. Currently, it is difficult to provide wavelength multicast over optical switches without optical/electronic conversions although the conversion takes extra cost. In this paper, based on the proposed wavelength router architecture (equipped with ATM switches to offer O/E and E/O conversions when necessary), a dynamic multicast routing algorithm is proposed to furnish multicast services over WDM networks. The goal is to join a new group member into the multicast tree so that the cost, including the link cost and the optical/electronic conversion cost, is kept as low as possible. The same algorithm can be applied to other wavelength routing architectures with redefinition of electronic copy cost. The effectiveness of the proposed wavelength router architecture as well as the dynamic multicast algorithm is evaluated by simulation.     

Flow of a viscoelastic shear-thinning fluid between two concentric rotating spheres

The flow of a viscoelastic fluid, which is simulated by a Criminale-Ericksen-Filbey model, between two concentric rotating spheres is analyzed theoretically. This problem has wide applications in practice. The assessment of the performance of a polymerization reactor, for example, requires knowledge about the rheological properties of the reacting fluids and flow patterns around agitators. We show that the shear-thinning effects of both the viscosity and the elasticity of a fluid may lead to double-vortex flows. The origin of these vortices are discussed, and the effect of the relative sizes of the inner and the outer spheres on the vortex flows is investigated. The influence of the elasticity on the torque required to rotate the spheres is also evaluated.