Correlation-aware packet scheduling in multi-camera networks

In multiview applications, multiple cameras acquire the same scene from different viewpoints and generally produce correlated video streams. This results in large amounts of highly redundant data. In order to save resources, it is critical to handle properly this correlation during encoding and transmission of the multiview data. In this work, we propose a correlation-aware packet scheduling algorithm for multi-camera networks, where information from all cameras are transmitted over a bottleneck channel to clients that reconstruct the multiview images. The scheduling algorithm relies on a new rate-distortion model that captures the importance of each view in the scene reconstruction. We propose a problem formulation for the optimization of the packet scheduling policies, which adapt to variations in the scene content. Then, we design a low complexity scheduling algorithm based on a trellis search that selects the subset of candidate packets to be transmitted towards effective multiview reconstruction at clients. Extensive simulation results confirm the gain of our scheduling algorithm when inter-source correlation information is used in the scheduler, compared to scheduling policies with no information about the correlation or non-adaptive scheduling policies. We finally show that increasing the optimization horizon in the packet scheduling algorithm improves the transmission performance, especially in scenarios where the level of correlation rapidly varies with time. © 2013 IEEE

Price-Based Controller for Utility-Aware HTTP Adaptive Streaming

HTTP Adaptive Streaming (HAS) permits to efficiently deliver video to multiple heterogenous users in a fully distributed way. This might however lead to unfair bandwidth utilization among HAS users. Therefore, network-assisted HAS systems have been proposed where network elements operate alongside with the clients adaptation logic for improving users satisfaction. However, current solutions rely on the assumption that network elements have full knowledge of the network status, which is not always realistic. In this work, we rather propose a practical network-assisted HAS system where the network elements infer the network link congestion using measurements collected from the client endpoints, the congestion level signal is then used by the clients to optimize their video data requests. Our novel controller maximizes the overall users satisfaction and the clients share the available bandwidth fairly from a utility perspective, as demonstrated by simulation results obtained on a network simulator

Finite Length Performance of Random Slotted ALOHA Strategies

Multiple connected devices sharing common wireless resources might create interference if they access the channel simultaneously. Medium access control (MAC) protocols gener- ally regulate the access of the devices to the shared channel to limit signal interference. In particular, irregular repetition slotted ALOHA (IRSA) techniques can achieve high-throughput performance when interference cancellation methods are adopted to recover from collisions. In this work, we study the finite length performance for IRSA schemes by building on the analogy between successive interference cancellation and iterative belief- propagation on erasure channels. We use a novel combinatorial derivation based on the matrix-occupancy theory to compute the error probability and we validate our method with simulation results

Interlimb transfer of unimanual grasping movement in upper limb amputees - A pilot study.

Background. Inter-hemispheric communication is necessary during uni- manual grip of an object (1). The right and left hands share a level of representation in the motor program that is common to both (2). It could be essential to take into consideration bi- hemispheric activity to adapt prosthesis of individuals with upper limb amputation.\ud Objective. To determine the relevance of the inter-hemispheric dependence in the programing and execution of uni-manual grip in individuals with upper limb amputation.\ud Methods. Five adults with amputation of the upper limb above and below the elbow participated in this study. Each participant was seated and asked to grab and lift an instrumented cylinder with the sound hand 15 times (Figure 1). The cylinder enabled to record in real time the apposition axis (AO) passing by the thrum, the centre of the cylinder and the first finger as well as the forces applied during the griping period of 2000 ms. The participants were assessed during the temporary (PP) and definitive (PD) phases of prosthesis fitting the after the amputation. Student t-tests were used to determine the effect of different prosthetic phases on the force and orientation of the griping hand.\ud Results\ud 1. A significant reduction (p<0.01) of the forces applied by the sound hand between the two prosthetic phase for 4/5 of the participants (Figure 2)\ud 2. Some changes in the gripping orientation when the amputated hand was dominant for 2/3 of the participants (Figure 3) 3. No changes in the gripping orientation when the amputated hand was not dominant\ud Conclusion. Grip programming and execution with sound hand:\ud 1. Change between two prosthetic fitting phases\ud 2. Depend on the inter-hemispheric transfer related to the force regardless on the amputated hand.\ud 3. Depend on the inter-hemispheric transfer related to the gripping orientation only when the amputated side is dominant.\ud Adjustments in griping force and orientation of the prosthesis depending on the grip correction of the sound hand might be respectively more necessary regardless of the amputated hand and when the amputated hand is dominant.\ud Because of the variability between participants concerning the side of amputation and manual dominance, other studies will be required to generalise these results

Introducing physician assistants into new roles: International experiences

Conference report: The development of physician assistants (PAs) is a phenomenon that has accelerated since the new century and many countries are involved (1). We report on countries that have recently introduced PAs to identify opportunities for improving the transition. The 35th Annual Physician Assistant Conference of the American Academy of Physician Assistant (AAPA) held in Philadelphia, US, May 26-31, 2007 was attended by almost 8,000 delegates including PAs, students, academics and policy makers. The main purposes of this conference were to promote professional development, develop ideas and provide education. It also featured an international forum focusing on global developments

Fertilization of Dioscorea rotundata with poultry manure: effects on nutrient dynamics and nutrient use efficiencies. Awarded poster presentation

Similar effects of poultry manure (PM) and mineral fertilizer suggest that PM is a cheap and effective alternative to fertilizers for yam production

Fertilization of Dioscorea rotundata with poultry manure: effects on nutrient dynamics and nutrient use efficiencies

Similar effects of poultry manure (PM) and mineral fertilizer suggest that PM is a cheap and effective alternative to fertilizers for yam production

Biomechanical analyses of the performance of Paralympians: From foundation to elite level

Biomechanical analysis of sport performance provides an objective method of determining performance of a particular sporting technique. In particular, it aims to add to the understanding of the mechanisms influencing performance, characterization of athletes, and provide insights into injury predisposition. Whilst the performance in sport of able-bodied athletes is well recognised in the literature, less information and understanding is known on the complexity, constraints and demands placed on the body of an individual with a disability. This paper provides a dialogue that outlines scientific issues of performance analysis of multi-level athletes with a disability, including Paralympians. Four integrated themes are explored the first of which focuses on how biomechanics can contribute to the understanding of sport performance in athletes with a disability and how it may be used as an evidence-based tool. This latter point questions the potential for a possible cultural shift led by emergence of user-friendly instruments. The second theme briefly discusses the role of reliability of sport performance and addresses the debate of two-dimensional and three-dimensional analysis. The third theme address key biomechanical parameters and provides guidance to clinicians, and coaches on the approaches adopted using biomechanical/sport performance analysis for an athlete with a disability starting out, to the emerging and elite Paralympian. For completeness of this discourse, the final theme is based on the controversial issues on the role of assisted devices and the inclusion of Paralympians into able-bodied sport is also presented. All combined, this dialogue highlights the intricate relationship between biomechanics and training of individuals with a disability. Furthermore, it illustrates the complexity of modern training of athletes which can only lead to a better appreciation of the performances to be delivered in the London 2012 Paralympic Games

AVALIAÇÃO DO DESEMPENHO DE TÉCNICAS PARA MELHORIA DA FORMULAÇÃO MECID EM PROBLEMAS DE AUTOVALOR

A técnica de Integração Direta (MECID) já se mostrou uma vertente adequada do Método dos Elementos de Contorno para resolver problemas expressos por equações diferenciais parciais, que apresentam termos que não são dados por operadores auto-adjuntos ou requeiram a utilização de uma solução fundamental que não é correlata ao problema proposto. Já foi utilizado anteriormente, de forma bem sucedida, em problemas governados pelas Equações de Poisson e de Helmholtz. Porém, todo método numérico passa por inúmeros processos de melhoria e essas visam aprimorar os resultados apresentados, adaptá-lo à solução de uma nova família de problemas, diminuir o seu custo computacional e até mesmo simplificá-lo matematicamente. Buscando melhorar a qualidade dos resultados apresentados pelo MECID, testam-se dois expedientes diferentes com essa finalidade: primeiramente, a utilização de diferentes famílias de Funções de Base Radial para analisar quais são as funções que permitem a obtenção de melhor precisão nos resultados; em segundo lugar, a utilização de um esquema de regularização do tipo proposto por Hadamard para remover a singularidade que ocorre no núcleo das integrais a serem interpoladas pela MECID, eliminando assim a necessidade de conjuntos distintos de pontos, um para interpolação e outro para geração de pontos fonte. A avaliação dos procedimentos é feita confrontando-se valores numéricos com os analíticos na solução de problemas bidimensionais de autovalor bem conhecidos