Appointed File Prefetching for Distributed File Systems

One of key issues in the design of distributed file systems is how to reduce the latency when accessing remote files, with the solutions including cache replacement and file-prefetching technologies. In this paper, we propose a novel method called appointed file prefetching, in which the main idea is to enable the user or system administrator to specify how to perform file prefetching. We define the appointed file-prefetching language (AFPL) that the user and system administrator can use to instruct the system to perform desired prefetching at appropriate times. The prefetching instructions in the AFPL can be divided into two categories: (1) selecting the required files and (2) specifying when to perform prefetching. According to the information in the file system and the previous file access records, a user can select the needed files as candidates for prefetching and then choose between time prefetching and event prefetching to retrieve them. The experimental results show that the waiting time of remote file fetching is reduced by 30 % to 90 % and the hit ratio is increased by 6 % to 18 % in most cases

Sistemas interativos e distribuídos para telemedicina

doutoramento Ciências da ComputaçãoDurante as últimas décadas, as organizações de saúde têm vindo a adotar continuadamente as tecnologias de informação para melhorar o funcionamento dos seus serviços. Recentemente, em parte devido à crise financeira, algumas reformas no sector de saúde incentivaram o aparecimento de novas soluções de telemedicina para otimizar a utilização de recursos humanos e de equipamentos. Algumas tecnologias como a computação em nuvem, a computação móvel e os sistemas Web, têm sido importantes para o sucesso destas novas aplicações de telemedicina. As funcionalidades emergentes de computação distribuída facilitam a ligação de comunidades médicas, promovem serviços de telemedicina e a colaboração em tempo real. Também são evidentes algumas vantagens que os dispositivos móveis podem introduzir, tais como facilitar o trabalho remoto a qualquer hora e em qualquer lugar. Por outro lado, muitas funcionalidades que se tornaram comuns nas redes sociais, tais como a partilha de dados, a troca de mensagens, os fóruns de discussão e a videoconferência, têm o potencial para promover a colaboração no sector da saúde. Esta tese teve como objetivo principal investigar soluções computacionais mais ágeis que permitam promover a partilha de dados clínicos e facilitar a criação de fluxos de trabalho colaborativos em radiologia. Através da exploração das atuais tecnologias Web e de computação móvel, concebemos uma solução ubíqua para a visualização de imagens médicas e desenvolvemos um sistema colaborativo para a área de radiologia, baseado na tecnologia da computação em nuvem. Neste percurso, foram investigadas metodologias de mineração de texto, de representação semântica e de recuperação de informação baseada no conteúdo da imagem. Para garantir a privacidade dos pacientes e agilizar o processo de partilha de dados em ambientes colaborativos, propomos ainda uma metodologia que usa aprendizagem automática para anonimizar as imagens médicasDuring the last decades, healthcare organizations have been increasingly relying on information technologies to improve their services. At the same time, the optimization of resources, both professionals and equipment, have promoted the emergence of telemedicine solutions. Some technologies including cloud computing, mobile computing, web systems and distributed computing can be used to facilitate the creation of medical communities, and the promotion of telemedicine services and real-time collaboration. On the other hand, many features that have become commonplace in social networks, such as data sharing, message exchange, discussion forums, and a videoconference, have also the potential to foster collaboration in the health sector. The main objective of this research work was to investigate computational solutions that allow us to promote the sharing of clinical data and to facilitate the creation of collaborative workflows in radiology. By exploring computing and mobile computing technologies, we have designed a solution for medical imaging visualization, and developed a collaborative system for radiology, based on cloud computing technology. To extract more information from data, we investigated several methodologies such as text mining, semantic representation, content-based information retrieval. Finally, to ensure patient privacy and to streamline the data sharing in collaborative environments, we propose a machine learning methodology to anonymize medical images

The Design and Implementation of Appointed File Prefetching for Distributed File Systems

Abstract. Many types of distributed file systems have been in widespread use for more than a decade. One of key issues in their design is how to reduce the latency when accessing remote files, with the solutions including cache replacement and file-prefetching technologies. In this paper, we propose a novel method called appointed file prefetching, in which the main idea is to enable the user or system administrator to specify how to perform file prefetching. We define the appointed file-prefetching language (AFPL) that the user and system administrator can use to instruct the system to perform desired prefetching at appropriate times. The prefetching instructions in the AFPL can be divided into two categories: (1) selecting the required files and (2) specifying when to perform prefetching. The experimental results show that the waiting time of remote file fetching is reduced by 30 % to 90 % and the hit ratio is increased by 6 % to 18 % in most cases