7,047 research outputs found
SHStream: Self-Healing Framework for HTTP Video-Streaming
HTTP video-streaming is leading delivery of video
content over the Internet. This phenomenon is explained by the
ubiquity of web browsers, the permeability of HTTP traffic
and the recent video technologies around HTML5. However,
the inclusion of multimedia requests imposes new requirements
on web servers due to responses with lifespans that can reach
dozens of minutes and timing requirements for data fragments
transmitted during the response period. Consequently, web-
servers require real-time performance control to avoid playback
outages caused by overloading and performance anomalies. We
present
SHStream
, a self-healing framework for web servers
delivering video-streaming content that provides (1) load admit-
tance to avoid server overloading; (2) prediction of performance
anomalies using online data stream learning algorithms; (3)
continuous evaluation and selection of the best algorithm for
prediction; and (4) proactive recovery by migrating the server
to other hosts using container-based virtualization techniques.
Evaluation of our framework using several variants of
Hoeffding
trees
and
ensemble algorithms
showed that with a small number of
learning instances, it is possible to achieve approximately 98% of
recall
and 99% of
precision
for failure predictions. Additionally,
proactive failover can be performed in less than 1 secon
Reboot-based Recovery of Performance Anomalies in Adaptive Bitrate Video-Streaming Services
Performance anomalies represent one common type
of failures in Internet servers. Overcoming these failures without
introducing server downtimes is of the utmost importance in
video-streaming services. These services have large user abandon-
ment costs when failures occur after users watch a significant part
of a video. Reboot is the most popular and effective technique for
overcoming performance anomalies but it takes several minutes
from start until the server is warmed-up again to run at its
full capacity. During that period, the server is unavailable or
provides limited capacity to process end-users’ requests. This
paper presents a recovery technique for performance anomalies
in HTTP Streaming services, which relies on Container-based
Virtualization to implement an efficient multi-phase server reboot
technique that minimizes the service downtime. The recovery
process includes analysis of variance of request-response times
to delimit the server warm-up period, after which the server
is running at its full capacity. Experimental results show that
the Virtual Container recovery process completes in
72
seconds,
which contrasts with the
434
seconds required for full operating
system recovery. Both recovery types generate service downtimes
imperceptible to end-users
Antecipar para Agir: Potencialidades da Análise Prospetiva para a Construção de “Novos Rumos” do Turismo na Sociedade de Risco
Este artigo tem a finalidade de mostrar como a análise prospetiva constitui uma ferramenta que pode potenciar as dimensões exploratória e estratégica do planeamento em turismo em contextos marcados pela mudança acelerada, o risco e outras incertezas e, nessa medida, auxiliar atores e stakeholders nos processos de definição e construção de
novos rumos para o turismo.
Os estudos prospetivos são hoje uma poderosa ferramenta na área do planeamento e assumem maior pertinência em tempos incertos, balizados pela complexidade e por inúmeros constrangimentos (mas também oportunidades) associados à globalização e à(s) crise(s) que afetam o sistema-mundo.
No domínio do Turismo, como noutros, além de informar as políticas, através dos diagnósticos prospetivos que realiza, a análise prospetiva pode potenciar a construção de redes de atores envolvidos na «modelação do futuro» na área da inovação social e, ainda, contribuir para desenvolver capacidades em toda a região no domínio do desenvolvimento de uma “cultura prospetiva”, reforçando o empowerment coletivo e as suas próprias redes.
Em síntese, o conhecimento de métodos, técnicas e formas de operacionalização da prospetiva por parte dos atores individuais e coletivos do setor turístico podem ser uma mais-valia diferenciadora e potenciadora de um planeamento estratégico mais informado, participado e partilhado
Ânforas da Villa Romana de Vilares de Alfundão (Ferreira do Alentejo)
Os autores estudam um conjunto anfórico recolhido nos restos conservados à superfície de uma villa romana, Vilares de Alfundão (Ferreira do Alentejo).
Da análise tipológica e do estudo das pastas cerâmicas, conclui-se que a maioria terá sido fabricada nos fornos do Baixo Sado, predominando largamente as formas Dressel 14b e Almagro 51c. Tais resultados são comparados e discutidos, especialmente com os obtidos do estudo das ânforas de S. Cucufate (Vidigueira). Em dois fundos de ânforas DresseI 14 aparece o mesmo grafito e um dos exemplares da forma Almagro 50 ostenta na asa a marca [ . .. ] CVRVCVNIN
An integrated investigation of the Rio tailings, Panasqueira mine, Centre Portugal
The risks associated with mine tailings have different nature and, thus, only a multiple approach can investigate and monitor comprehensively the characteristics and evolution of mine tailings impacts on the environment.
Deposition at the Rio tailings (Panasqueira Mine) lasted about ninety years. Over one million cubic metres, of complex very fine to fine material, are deposited on a mountain side overlaying the Zezere river, increasing the risk of contamination of one of the most important hydrographic basins in central Portugal.
Herein, a multidisciplinary study including geophysics, geochemistry and borehole information, organized in a GIS, is used to characterize the Rio tailings.
The geophysical survey comprised ERT (Electrical Resistivity Tomography) and GPR (Ground Penetrating Radar) on the mud impoundment, as well as, on the slope of the tailings. The geochemical survey consisted on collecting water and tailings samples, iron coatings, arsenopyrite stockpile material and ferruginous crust. Samples collected in boreholes, drilled specifically for this project, were also analyzed.
The GIS provided imaging of the geophysical, geochemical and particle size spatial distribution, so that comparisons between the different data sets are easily done. Resistivity and GPR allowed bedrock positioning. GPR was able to give layering results within the tailings.
Finally, comparison and correlation between geophysical and geochemical results are carried out and evaluated on the GIS platform
Production and characterization of mead from the honey of Melipona scutellaris stingless bees
The Institute of Brewing & Distilling Mead is a traditional alcoholic beverage obtained by fermenting must and can offer a solution to honey over-production and a way of valorizing honey of lower quality. The purpose of this study was to produce and characterize mead with different levels of sugars and alcohol obtained from honey from Melipona scutellaris. The honey used for mead preparation was analysed in order to ensure that it met the required quality standards. It was found that the alcoholic content and volatile acidity were outwith the limits established by Brazilian law. Mead legislation is based on the product obtained from Apis mellifera (‘honey bee’) honey and these results indicate the need to re-evaluate the standards established for this product in order to incorporate mead produced from honey from stingless bees of the genus Melipona. Copyright © 2018 The Institute of Brewing & Distilling.We thank the Coordination for the Improvement of Higher
Education Personnel (Coordenação de Aperfeiçoamento de
Pessoal de Nível Superior) for granting a scholarship of the Institutional
Program of Scholarships of Doctorate Sandwich Abroad
to Samira Maria Peixoto Cavalcante da Silva, financial support
for the project and a scholarship granted to Leticia M. Estevinho.
We also thank the National Council for Scientific and Technological
Development (Conselho Nacional de Desenvolvimento Científico e
Tecnológico) for a research scholarship granted to Carlos Alfredo
Lopes de Carvalho. We thank the Polytechnic Institute of Bragança,
in particular to the Laboratory of Microbiology, for the development
of the work. This work was supported by the strategic
programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569)
funded by national funds through the FCT IP and by the ERDF
through the COMPETE2020 – Programa Operacional
Competitividade e Internacionalização.info:eu-repo/semantics/publishedVersio
Osteoporosis management during the COVID-19 pandemic - Position paper
verCOVID-19 pandemic significantly increased the already large number of victims of osteoporosis in Portugal. Osteoporosis outpatient clinics were either closed or had limited presential appointments. Many hospitals reduced orthopaedic services to make space for patients with COVID-19. In addition, the volunteer or forced sedentarism, as imposed by the pandemic, increased the risk of falls and fractures drastically. It urges to intensify the current efforts to improve the management of bone health and to prioritize fragility fracture care and prevention. This paper addresses the challenges in osteoporosis management during the COVID-19 pandemic and provides guidance on osteoporosis management. This position paper is a joint initiative of several health professionals and patients dedicated to osteoporosis.publishersversionpublishe
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