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
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.
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...
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.
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.
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.
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)...
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...
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...
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
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
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).
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
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...
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
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.
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...
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.
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.
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