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In the preparation of Caf\'e Latte, spectacular layer formation can occur between the expresso shot in a glass of milk and the milk itself. Xue et al. (Nat. Commun., vol. 8, 2017, pp. 1-6) showed that the injection velocity of expresso determines the depth of coffee-milk mixture. After a while when a stable stratification forms in the mixture, the layering process can be modelled as a double diffusive convection system with a stably-stratified coffee-milk mixture cooled from the side. More specifically, we perform (two-dimensional) direct numerical simulations of laterally cooled double diffusive convection for a wide parameter range, where the convective flow is driven by a lateral temperature gradient while stabilized by a vertical concentration gradient. When the thermal driving force dominates over the stabilizing force, the flow behaves like vertical convection in which a large-scale circulation develops. However, with increasing strength of the stabilizing force, a meta-stable layered regime emerges. Initially, several vertically-stacked convection rolls develop, and these well-mixed layers are separated by sharp interfaces with large concentration gradients. The initial thickness of these emerging layers can be estimated by balancing the work exerted by thermal driving and the required potential energy to bring fluid out of its equilibrium position in the stably stratified fluid. In the layered regime, we further observe successive layer merging, and eventually only a single convection roll remains. We elucidate the following merging mechanism: As weakened circulation leads to accumulation of hot fluid adjacent to the hot sidewall, larger buoyancy forces associated with hotter fluid eventually break the layer interface. Then two layers merge into a larger layer, and circulation establishes again within the merged structure., Comment: 10 pages, 4 figures

In this paper, a transmission strategy of fountain codes over cooperative relay networks is proposed. When more than one relay nodes are available, we apply network coding to fountain-coded packets. By doing this, partial information is made available to the destination node about the upcoming message block. It is therefore able to reduce the required number of transmissions over erasure channels, hence increasing the effective throughput. Its application to wireless channels with Rayleigh fading and AWGN noise is also analysed, whereby the role of analogue network coding and optimal weight selection is demonstrated.

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices., Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004 issue, Journal of Applied Physics

LaAlO3-Ba0.5Sr0.5TiO3 (LAO-BST) thin films, with different LAO contents, were deposited on Pt/Ti/SiO2/Si and (100) LaAlO3 substrate, via a pulsed laser deposition (PLD). Phase composition and microstructure of the LAO-BST thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LAO-BST thin films were solid solution of LAO nd BST, with lattice constant decreasing with increasing LAO content. The composition of (LAO)x(BST)1-x, estimated from the lattice constant of the thin films derived from the targets of 1/6, 2/6 and 3/6 LAO, was 0.143, 0.278, 0.476, respectively. The grain size of the thin films decreased as a result of the incorporation of LAO into BST. Dielectric properties of the LAO-BST thin films on Pt/Ti/SiO2/Si were measured at low frequency (100 kHz), while those on LaAlO3 substrate were characterized at high frequency (~7.9 GHz). The dielectric constants of the film derived from pure BST target and those from the targets with 1/6, 2/6 and 3/6 area ratio of LAO, on Pt/Ti/SiO2/Si substrate, were 772, 514, 395 and 282, with a dielectric loss of 0.096, 0.023, 0.024 and 0.025, and a dielectric tunability of 65%, 53%, 43% and 14%, respectively. The dielectric constant of the LAO-BST films on LaAlO3 substrate were 2436, 2148, 2018, 1805, with a maximum dielectric tunability of 11%, 13%, 10% and 8% at a maximum applied voltage of 2.4 kV (~9.2 kV/cm)., Comment: 19 pages, 9 figures

Fractal behavior and long-range dependence have been observed in tele-traffic measurement and characterization. In this paper we show results of application of the fractal analysis to internet traffic via various methods. Our result demonstrate that the internet traffic exhibits self-similarity. Time-scale analysis show to be an effective way to characterize the local irregularity. Based on the result of this study, these two Internet time series exhibit fractal characteristic with long-range dependence., Comment: 10 pages, 6 figures