Página 1 dos resultados de 361 itens digitais encontrados em 0.002 segundos

Sinalização de media gateways em redes de próxima geração

Silva, André Marques e
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
27.24%
Com o grande crescimento das comunicações móveis e fixas, o acesso à Internet tornou-se cada vez mais numa exigência, colocando à industria das Telecomunicações, especialmente aos operadores, grandes desafios. Serviços comuns como chamadas de voz, podem agora ser oferecidos pelos Internet Service Providers (ISPs) aos seus clientes sobre a forma de serviço Voice over IP (VoIP). Este serviço deixou de ser exclusivo das redes Public Switched Telephone Network/Integrated Services Digital Network (PSTN/ISDN) e passou a ser fornecido também na Internet. Mas devido à necessidade de manter as tradicionais redes PSTN/ISDN, houve a necessidade de criar um ambiente de convergência, não só para estas redes mas também para outros tipos de redes de acesso, independentemente da tecnologia. É neste campo que os organismos de normalização e os operadores têm dado os seus contributos, criando uma rede de controlo e de transporte comum baseada em IP para a convergência de serviços. Inicialmente o 3rd Generation Partnership Project (3GPP) definiu uma arquitectura de convergência móvel com a rede IP, constituída por elementos de controlo, transporte e serviço, de nome IP Multimedia Subsystem (IMS). Mais tarde, esta arquitectura serviu de base (core) para o grupo TISPAN do European Telecommunications Standard Institute (ETSI) na normalização das Redes de Próxima Geração. Esta Dissertação pretende dar uma resposta à convergência fixo-móvel no âmbito da arquitectura PSTN/ISDN Emulation Subsystem (PES) do TISPAN. Este sistema permite que todos os clientes de uma Rede de Próxima Geração de um operador acedam a serviços das redes PSTN/ISDN e Digital Subscriber Line (DSL) de uma forma simples e imperceptível. Com este intuito foram desenvolvidos cenários de testes para os sistemas Trunking e de Acesso da arquitectura PES...

Residential Segregation in Metropolitan Established Immigrant Gateways and New Destinations, 1990–2000*

Park, Julie; Iceland, John
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/2011 Português
Relevância na Pesquisa
27.24%
In the 1990s, many immigrants bypassed established gateways like Los Angeles, New York, Chicago, and Miami to create new immigrant destinations across the U.S. In this paper, we examine how segregation and spatial assimilation might differ between established gateways and new destinations among the 150 largest metropolitan areas. Using data from the 1990 and 2000 censuses, we calculate levels of dissimilarity for Hispanics and Asians by nativity for these two gateway types. Our findings show that segregation levels are consistently lower in new destinations. However, Hispanics in new destinations experienced significant increases segregation during the 1990s, suggesting a convergence in residential patterns by destination type. Nevertheless, in both destinations the native-born are less segregated than the foreign born—consistent with immigrant spatial incorporation. Finally, socioeconomic indicators are generally consistent with predictions of spatial assimilation.

Protocole de routage basé sur des passerelles mobiles pour un accès Internet dans les réseaux véhiculaires

Ba, Amadou Adama
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
27.24%
La rapide progression des technologies sans fil au cours de ces dernières années a vu naître de nouveaux systèmes de communication dont les réseaux véhiculaires. Ces réseaux visent à intégrer les nouvelles technologies de l’information et de la communication dans le domaine automobile en vue d’améliorer la sécurité et le confort sur le réseau routier. Offrir un accès Internet aux véhicules et à leurs occupants peut sans doute aider à anticiper certains dangers sur la route tout en rendant plus agréables les déplacements à bord des véhicules. Le déploiement de ce service nécessite que des messages soient échangés entre les véhicules. Le routage constitue un élément crucial dans un réseau, car définissant la façon dont les différentes entités échangent des messages. Le routage dans les VANETS constitue un grand défi car ces derniers sont caractérisés par une forte mobilité entraînant une topologie très dynamique. Des protocoles ont été proposés pour étendre Internet aux réseaux véhiculaires. Toutefois, la plupart d’entre eux nécessitent un coût élevé de messages de contrôle pour l’établissement et le maintien des communications. Ceci a pour conséquence la saturation de la bande passante entrainant ainsi une baisse de performance du réseau. Nous proposons dans ce mémoire...

A Credential Store for Multi-tenant Science Gateways

Kanewala, Thejaka Amilia; Marru, Suresh; Basney, Jim; Pierce, Marlon
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Relatório
Português
Relevância na Pesquisa
37.62%
Science Gateways bridge multiple computational grids and clouds, acting as overlay cyberinfrastructure. Gateways have three logical tiers: a user interfacing tier, a resource tier and a bridging middleware tier. Different groups may operate these tiers. This introduces three security challenges. First, the gateway middleware must manage multiple types of credentials associated with different resource providers. Second, the separation of the user interface and middleware layers means that security credentials must be securely delegated from the user interface to the middleware. Third, the same middleware may serve multiple gateways, so the middleware must correctly isolate user credentials associated with different gateways. We examine each of these three scenarios, concentrating on the requirements and implementation of the middleware layer. We propose and investigate the use of a Credential Store to solve the three security challenges.

Cyberinfrastructure, Science Gateways, Campus Bridging, and Cloud Computing

Stewart, Craig A.; Knepper, Richard D.; Link, Matthew R.; Pierce, Marlon; Wernert, Eric A.; Wilkins-Diehr, Nancy
Fonte: IGI Global Publicador: IGI Global
Tipo: Parte de Livro
Português
Relevância na Pesquisa
37.24%
Computers accelerate our ability to achieve scientific breakthroughs. As technology evolves and new research needs come to light, the role for cyberinfrastructure as “knowledge” infrastructure continues to expand. This article defines and discusses cyberinfrastructure and the related topics of science gateways and campus bridging; identifies future challenges in cyberinfrastructure; and discusses challenges and opportunities related to the evolution of cyberinfrastructure, “big data” (datacentric, data-enabled, and data-intensive research and data analytics), and cloud computing.; This material is based upon work supported by the National Science Foundation under grants 0504075, 0451237, 0723054, 1062432, 0116050, 0521433, 0503697, and 1053575, and several IBM Shared University Research grants and support provided by Lilly Endowment, Inc. for the Indiana University Pervasive Technology Institute. Any opinions, findings and conclusions or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the supporting agencies.

Apache Airavata: Design and Directions of a Science Gateway Framework

Pierce, Marlon E.; Marru, Suresh; Gunathilake, Lahiru; Kanewala, Thejaka Amilia; Singh, Raminder; Wijeratne, Saminda; Wimalasena, Chathuri; Herath, Chathura; Chinthaka, Eran; Mattmann, Chris; Slominski, Aleksander; Tangchaisin, Patanachai
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Relatório
Português
Relevância na Pesquisa
27.42%
This paper provides an overview of the Apache Airavata software system for science gateways. Gateways use Airavata to manage application and workflow executions on a range of backend resources (grids, computing clouds, and local clusters). Airavata???s design goal is to provide component abstractions for major tasks required to provide gateway application management. Components are not directly accessed but are instead exposed through a client Application Programming Interface. This design allows gateway developers to take full advantage of Airavata???s capabilities, and Airavata developers (including those interested in middleware research) to modify Airavata???s implementations and behavior. This is particularly important as Airavata evolves to become a scalable, elastic ???platform as a service??? for science gateways. We illustrate the capabilities of Airavata through the discussion of usage vignettes. As an Apache Software Foundation project, Airavata???s open community governance model is as important as its software base. We discuss how this works within Airavata and how it may be applicable to other distributed computing infrastructure and cyberinfrastructure efforts.

Experiences Developing Tools for Scientific Communities in the Apache Software Foundation: Beyond Open Source

Pierce, Marlon
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
27.24%
Presented at XSEDE Extended Collaborative Support Service symposium teleconference.; Science Gateways provide Web-based environments for scientists and students to perform computational experiments online via Web interfaces using Web services and computational workflows. Gateways rely on open source software, and many gateway developers have taken the extras step to make their own software open source, using tools like SourceForge, Github, and Google Code to make their codes available, easy to find, and open licensed. However, we believe there are important steps that should be taken to go beyond basic open source to address requirements for building open software communities. In addition to licensing and support tools, open communities must have open processes for making design decisions, accepting code contributions, adding new project members, reporting and resolving problems, and making well-packaged and properly licensed software releases. The Apache Software Foundation provides the infrastructure and mentoring experience to help open source communities address these project governance issues. Additionally, Apache has an interesting requirements (such as developer diversity) that are designed to emphasize the neutrality of the code base (encouraging competitors to have a safe place to cooperate)...

Science Gateway Group Overview

Pierce, Marlon E.; Marru, Suresh; Singh, Raminder
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
27.24%
Presentation to CREST, Indiana University Pervasive Technology Institute.; We present an overview of the Science Gateways Group, part of UITS's Research Technologies division. The mission of the Science Gateway Group is to develop free, open source and open community software that can be used to provide Web-based access to clusters, supercomputers, computing clouds, and other elements of cyberinfrastructure. Scientific workflows are an important component of Science Gateways, supporting the composition and execution of chains of independently developed (sequential and parallel) scientific applications. Apache Airavata is our team's scientific workflow software, which we use to support a number of collaborations and extended consulting activities as part of our participation in the NSF XSEDE program. Through these collaborations with application scientists in nuclear physics, astronomy, astrophysics, biophysics, and other fields, we are starting to identify general workflow execution patterns that go beyond simple chain and directed acyclic graph execution scenarios. We believe this work is complementary to the research work at CREST and would like to investigate opportunities for collaboration. We are advocates for the Apache Software Foundation's open model for community building and also discuss the implications of this on cyberinfrastructure software.; The material of this presentation is based on work supported by the National Science Foundation under Grant NSF OCI Award 1032742...

Web-Based Science Gateways for Structural Bioinformatics; Webbasierte Science Gateways für Strukturbioinformatik

Gesing, Sandra
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
Português
Relevância na Pesquisa
27.88%
Structural bioinformatics applies computational methods to analyse and model three-dimensional molecular structures. These methods address data-intensive and compute-intensive problems, which demand high-performance computing (HPC) to allow data analysis in an acceptable time. Thus, structural bioinformatic applications are ideal candidates for grid and cloud computing infrastructures, so-called DCIs (Distributed Computing Infrastructures). DCIs provide access to HPC facilities and services across organisational boundaries. However, the usability of DCIs is limited and the use of the complex methods in structural bioinformatics requires a lot of experience. In addition, users mainly process and analyse data not only via single jobs but via workflows. An approach to offer easy and intuitive access to applications on DCIs are science gateways. In general, a science gateway provides a single point of entry to a set of tools and data of a specific application domain while hiding the complex underlying infrastructure. Web-based science gateways are additionally characterised by only requiring a computer connected to the Internet and an installed web browser on the users' side. Developers of such gateways support the users with pre-configured user interfaces targeted for a specific application domain. The overall goal for creating science gateways is to increase the usability of applications. This work is focused on workflow-enabled grid portals that are specific web-based science gateways supporting the management of workflows on DCIs. Four major aspects in the context of workflow-enabled grid portals are addressed in this work: security in portals with underlying DCIs...

Lao PDR : Trade and Transport Facilitation Assessment

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Other Urban Study; Economic & Sector Work
Português
Relevância na Pesquisa
27.24%
In Lao People's Democratic Republic (PDR), the value of trade has risen rapidly over the last decade with both imports and exports increasing by average annual rate of 24 percent. This report examines the trade logistics of Lao PDR. A trade and transport facilitation assessment was performed using a standardized toolkit and methodology developed by the World Bank to evaluate the quality of the logistics services. The assessment focused on the services used by these trades and the corridors used by these services. The assessment gave specific attention to two constraints on trade, the location of the country and the size of the trade. The study is organized in three interrelated parts: assessing the performance of the logistics sector; the international trade corridors linking Lao PDR to trade gateways in Thailand; and the supply chains used for distribution of exports. This report is presented in four sections. The first part examines the foreign trade of Lao PDR, the opportunities for growth and the logistics services in the movement of imports and exports between the country and its major gateways. The second section evaluates the performance of the corridors connecting the major origins and destinations in the country and the principal seaport used for international trade. The third section analyses the structure and performance characteristics of the supply chains used for selected trades and the implications for restructuring to support growth in the export trade. The final section presents a series of recommendations for improving the competitiveness of the exports through improvements in the structure of the supply chains...

Assessing Immigrant Assimilation: New Empirical and Theoretical Challenges

Waters, Mary; Jimenez, Tomas R.
Fonte: Annual Reviews Publicador: Annual Reviews
Português
Relevância na Pesquisa
27.24%
This review examines research on the assimilation of immigrant groups. We review research on four primary benchmarks of assimilation: socioeconomic status, spatial concentration, language assimilation, and intermarriage. The existing literature shows that today's immigrants are largely assimilating into American society along each of these dimensions. This review also considers directions for future research on the assimilation of immigrant groups in new southern and midwestern gateways and how sociologists measure immigrant assimilation. We document the changing geography of immigrant settlement and review the emerging body of research in this area. We argue that examining immigrant assimilation in these new immigrant gateways is crucial for the development of theories about immigrant assimilation. We also argue that we are likely to see a protracted period of immigrant replenishment that may change the nature of assimilation. Studying this change requires sociologists to use both birth cohort and generation as temporal markers of assimilation.; Sociology

Security for science gateways and campus bridging: XSEDE12 panel (extended abstract)

Basney, Jim; Butler, Randy; Fraser, Dan; Marru, Suresh; Stewart, Craig A.
Fonte: ACM Publicador: ACM
Tipo: Pré-impressão
Português
Relevância na Pesquisa
37.24%
This is a preprint of the extended abstract of a Birds of a Feather panel presented at the XSEDE12 conference, held July 16-19, 2012 in Chicago, IL. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.; The XSEDE 12 Panel Discussed Security for Science Gateways, Campus Bridging and discussed year 2 focus on Security Guidelines, Rocks Rolls Software Distribution, InCommon Authentication.; This material is based upon work supported by the National Science Foundation under Grants No OCI-1053575 to Extreme Science and Engineering Discovery Environment (XSEDE).

Gateways towards quasicrystals

Kramer, Peter
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/12/2010 Português
Relevância na Pesquisa
27.24%
The experimental discovery of quasicrystals by D Shechtman, D Gratias, I Blech, and J W Cahn in 1984 provided the paradigm for a new type of long-range order of solid matter in nature. This discovery stimulated an explosion of new experimental and theoretical research. In years prior to the discovery, there was a very active development of various gateways to quasicrystals in theoretical and mathematical physics. Without this conceptual basis, it would have been impossible to grasp and explore efficiently the structure and physical properties of quasicrystrals. The aim in what follows is to give a non-technical and condensed account of the conceptual gateways to quasicrystals prior to their discovery.; Comment: 17 pages, 5 figures

Model Driven Engineering for Science Gateways

Manset, David; McClatchey, Richard; Verjus, Herve
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/02/2014 Português
Relevância na Pesquisa
27.54%
From n-Tier client/server applications, to more complex academic Grids, or even the most recent and promising industrial Clouds, the last decade has witnessed significant developments in distributed computing. In spite of this conceptual heterogeneity, Service-Oriented Architectures (SOA) seem to have emerged as the common underlying abstraction paradigm. Suitable access to data and applications resident in SOAs via so-called Science Gateways has thus become a pressing need in various fields of science, in order to realize the benefits of Grid and Cloud infrastructures. In this context, authors have consolidated work from three complementary experiences in European projects, which have developed and deployed large-scale production quality infrastructures as Science Gateways to support research in breast cancer, paediatric diseases and neurodegenerative pathologies respectively. In analysing the requirements from these biomedical applications the authors were able to elaborate on commonly faced Grid development issues, while proposing an adaptable and extensible engineering framework for Science Gateways. This paper thus proposes the application of an architecture-centric Model-Driven Engineering (MDE) approach to service-oriented developments...

Towards Bridging IoT and Cloud Services: Proposing Smartphones as Mobile and Autonomic Service Gateways

Golchay, Roya; Mouël, Frédéric Le; Frénot, Stéphane; Ponge, Julien
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/07/2011 Português
Relevância na Pesquisa
27.24%
Computing is currently getting at the same time incredibly in the small with sensors/actuators embedded in our every- day objects and also greatly in the large with data and ser- vice clouds accessible anytime, anywhere. This Internet of Things is physically closed to the user but suffers from weak run-time execution environments. Cloud Environments provide powerful data storage and computing power but can not be easily accessed and integrate the final-user context- awareness. We consider smartphones are set to become the universal interface between these two worlds. In this position paper, we propose a middleware approach where smartphones provide service gateways to bridge the gap between IoT services and Cloud services. Since smartphones are mobile gateways, they should be able to (re)configure themself according to their place, things discovered around, and their own resources such battery. Several issues are discussed: collaborative event-based context management, adaptive and opportunistic service deployment and invocation, multi-criteria (user- and performance-oriented) optimization decision algorithm.; Comment: Position Paper

NFV Based Gateways for Virtualized Wireless Sensors Networks: A Case Study

Mouradian, Carla; Saha, Tonmoy; Sahoo, Jagruti; Glitho, Roch; Morrow, Monique; Polakos, Paul
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/03/2015 Português
Relevância na Pesquisa
27.24%
Virtualization enables the sharing of a same wireless sensor network (WSN) by multiple applications. However, in heterogeneous environments, virtualized wireless sensor networks (VWSN) raises new challenges such as the need for on-the-fly, dynamic, elastic and scalable provisioning of gateways. Network Functions Virtualization (NFV) is an emerging paradigm that can certainly aid in tackling these new challenges. It leverages standard virtualization technology to consolidate special-purpose network elements on top of commodity hardware. This article presents a case study on NFV based gateways for VWSNs. In the study, a VWSN gateway provider, operates and manages an NFV based infrastructure. We use two different brands of wireless sensors. The NFV infrastructure makes possible the dynamic, elastic and scalable deployment of gateway modules in this heterogeneous VWSN environment. The prototype built with Openstack as platform is described.

Pasarelas temáticas en internet: un modelo de directorio basado en la aplicación de técnicas documentales

Rodríguez Yunta, Luis
Fonte: Universitat Pompeu Fabra Publicador: Universitat Pompeu Fabra
Tipo: Artículo Formato: 183337 bytes; application/pdf
Português
Relevância na Pesquisa
27.54%
Copyright by UPF.-- La versión final está disponible en: http://www.hipertext.net; [ES] Pasarelas temáticas en Internet: un modelo de directorio basado en la aplicación de técnicas documentales. Como afirman Abadal y Estivill: "facilitar el acceso a un conjunto seleccionado de recursos web se puede considerar una tendencia plenamente consolidada en las bibliotecas de los países avanzados". Para ello pueden optar por tres opciones: 1) incluir en sus propios catálogos registros relativos a estos recursos, siguiendo las posibilidades que ofrecen los sistemas de gestión bibliotecaria; 2) crear guías de recursos de estructura sencilla y con una descripción elemental; 3) diseñar bases de datos más complejas específicamente diseñadas para la descripción de recursos seleccionados. En este artículo se analiza esta tercera opción, como un modelo concreto de directorio que ha sido desarrollado en bibliotecas, centros de documentación o consorcios de estas instituciones. Este modelo se denomina habitualmente como Subject Gateways (pasarelas temáticas). Se trata de sistemas de información que seleccionan, describen y clasifican recursos web aplicando criterios propios de la Biblioteconomía y Documentación, como las clasificaciones disciplinares o los lenguajes controlados. Para Sebastià y Martínez-Carner...

A Grid authorization model for science gateways

Scavo, Tom; Welch, Von
Fonte: Grid Computing Environments (GCE) Publicador: Grid Computing Environments (GCE)
Tipo: Proceedings
Português
Relevância na Pesquisa
27.42%
Since the number of TeraGrid Science Gateways is expected to grow at least an order of magnitude in the next few years, a lightweight gateway deployment model is sought, one that facilitates growth but meets the security requirements of the TeraGrid. To this end, we present a new authorization model for science gateways based on the community account model. This authorization model significantly increases the information flow between the gateway and the resource provider, without requiring new wire protocols or extensive new middleware infrastructure. Instead, the model complements existing technology and promises to leverage emerging federated identity deployments directly.; "A Grid authorization model for science gateways," Proceedings of the Grid Computing Environments (GCE) workshop. Held at the Reno Convention Center: Reno, Nevada: 11-12 November 2007.

Python for scientific gateways development

Heiland, Randy; Mooney, Sean; Boverhof, Joshua; Jackson, Keith; Swat, Maciek; Balter, Ariel; Christie, Marcus; Insley, Joseph
Fonte: Grid Computing Environments (GCE) Publicador: Grid Computing Environments (GCE)
Tipo: Proceedings
Português
Relevância na Pesquisa
37.24%
A scientific gateway is an interface that addresses some fundamental needs of a scientific community. This typically involves remote computation and/or data access. The interface might be Web-based or it might be some other type of workstation application that uses client-server technology. This paper focuses on tools and technologies that are based on the Python programming language and can be quite useful for scientific gateway development.; "Python for scientific gateways development," Proceedings of the Grid Computing Environments (GCE) workshop. Held at the Reno Convention Center: Reno, Nevada: 11-12 November 2007.

Science gateways on the TeraGrid: A survey of issues for deployment of community gateway interfaces to shared high-end computing resources

Catlett, Charlie; Goasguen, Sebastien; Marsteller, Jim; Martin, Stuart; Middleton, Don; Price, Kevin J.; Shankar, Anurag; Welch, Von; Wilkins-Diehr, Nancy
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Pré-impressão
Português
Relevância na Pesquisa
37.24%
Increasingly, the scientific community has been using web portals and desktop applications to organize their work. The TeraGrid team determined that it would be important to create a set of capabilities that would allow TeraGrid services and resources to be integrated, potentially in a transparent way, with these scientific computing environments. This paper outlines the “Science Gateways” program and provides an overview of key lessons learned in developing mechanisms to allow for such integration.; ACM, IEEE