Empirical evaluation of H.264/SVC streaming in resource-constrained multihomed mobile networks

Nomadic users of streamed multimedia content in mobile networks are often faced with resource-constrained network paths that suffer from low bandwidth. Streaming high-quality video in such a challenging scenario demands a set of highly adaptive schemes, which have not been sufficiently explored in particular for the emerging H.264 Scalable Video Coding (H.264/SVC) standard. In this paper, we empirically investigate the performance of streaming H.264/SVC scalable video streams to users in multihomed mobile networks containing multiple available transmission paths. Previous work has demonstrated the feasibility of aggregating bandwidth of multiple paths to deliver video streams when no single, sufficiently high bandwidth path is available. We focus on evaluating the enhanced performance of multipath bandwidth-aggregation streaming by exploiting a quality-layers based, H.264/SVC-specific packet prioritisation scheme for quality-aware multipath packet scheduling and selective packet dropping in case of bandwidth shortage even after aggregation. Additionally, we explore a base-layer rate control scheme for H.264/SVC delivery in ultra-low bandwidth environments. Through extensive experimentation on a realistic hardware-based testbed, we obtain a comprehensive and insightful understanding of the behaviour of H.264/SVC streams when transmitted across multiple paths in mobile networks. We quantify the improvements offered by the use of H.264/SVC-specific packet prioritisation schemes compared with an existing generic scalable video prioritisation scheme, and the benefits by the use of base-layer rate control in ultra-low bandwidth situations. The performance of the multipath streaming schemes is further compared with that of an ideal single high bandwidth path. We also identify the remaining challenges that must be overcome if such streaming schemes are to offer performance close to that of the ideal single high bandwidth path.     

Assessment of the MODIS LAI product for Australian ecosystems

The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the “space of canopy realisation” for savanna and broadleaf forest classes.     

The response of the adult and ATD heads to impacts onto a rigid surface

Given the high incidence of TBI, head injury has been studied extensively using both cadavers and anthropomorphic test devices (ATDs). However, few studies have benchmarked the response of ATD heads against human data. Hence, the objective of this study is to investigate the response of adult and ATD heads in impact, and to compare adult Hybrid III head responses to the adult head responses.     

Economies of scale in experimentation: knowledge and technology in pharmaceutical R&D

This paper explores how changes in genetics, database, high-throughputscreening and bioinformatics technologies have allowed pharmaceuticalfirms to exploit economies of scale in experimentation. Traditionalcraft-based, sequential experimentation in chemistry and biologyhas been complemented by firstly, the automated, mass-productionanalysis of populations and secondly, by 'in silico' experimentationusing simulations and databases. The changes are analysed withina Chandlerian framework that highlights how increases in the'throughput' of R&D are dependent on organizational andmanagerial responses to systemic uncertainty.     

Microstructural Development during the Microwave Sintering of Yttria—Zirconia Ceramics

The microstructural development of 3 and 8 mol% yttria—zirconia ceramics during microwave sintering was studied and compared to conventionally heated samples. Microwave heating enhanced the densification processes occurring during constant-rate heating for both materials. No change was found in the grain size—density relationship for the 8 mol% yttria—zirconia. However, a small, but statistically significant shift favoring densification was found for the 3 mol% yttriazirconia. Differences in the responses of the two materials are not completely understood but may be due to the differences in the activation energy for grain growth and grain-boundary mobility.     

A preliminary evaluation of the effects of primary and secondaryradiation forces on acoustic contrast agents

Primary and secondary radiation forces result from pressure gradients in the incident and scattered ultrasonic fields. These forces and their dependence on experimental parameters are described, and the theory for primary radiation force is extended to consider a pulsed traveling wave. Both primary and secondary radiation forces are shown to have a significant effect on the flow of microbubbles through a small vessel during insonation. The primary radiation force produces displacement of microspheres across a 100 micron vessel radius for a small transmitted acoustic pressure. The displacement produced by primary radiation force is shown to display the expected linear dependence on the pulse repetition frequency and a nonlinear dependence on transmitted pressure. The secondary radiation force produces a reversible attraction and aggregation of microspheres with a significant attraction over a distance of approximately 100 microns. The magnitude of the secondary radiation force is proportional to the inverse of the squared separation distance, and thus two aggregates accelerate as they approach one another. We show that this force is sufficient to produce aggregates that remain intact for a physiologically appropriate shear rate. Brief interruption of acoustic transmission allows an immediate disruption of the aggregate