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Diagnóstico automático de redes Profibus; Automatic diagnosis for Profibus networks

Mossin, Eduardo André
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/09/2012 Português
Relevância na Pesquisa
45.8%
Esta tese propõe a utilização de sistemas inteligentes para, automaticamente, realizar diagnósticos e localizar falhas na instalação e na operação de redes de comunicação industrial que utilizam o protocolo Profibus DP. Para tais tarefas, uma série de análises é realizada a partir dos sinais transmitidos pela camada física, de telegramas transmitidos pela camada de enlace e de funções da camada de usuário do protocolo Profibus DP. Para a análise da camada física, amostras dos sinais elétricos transmitidos são processadas e apresentadas a algumas Redes Neurais Artificiais para que sejam classificadas de acordo com a sua forma de onda. Caso estes sinais apresentem alguma deformação, o sistema indica uma provável causa para o problema, afinal, os problemas das redes Profibus originam padrões específicos e característicos impressos nas formas de onda do sinal digital. Ainda através da análise das amostras dos sinais oriundos da camada física, algumas fontes de problemas são detectadas a partir da análise do nível médio de tensão do sinal que um determinado dispositivo está transmitindo. Tal análise é realizada a partir de um Sistema Especialista. Também utilizando Sistemas Especialistas, os telegramas transmitidos pela camada de enlace deste protocolo são analisados e a partir destes...

Redes de comunicação e território: a formação e a organização socioespacial da internet no Brasil; Communication networks and territory: internet's formation and spatial organization in Brazil

Alves, Ludmila Girardi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/11/2013 Português
Relevância na Pesquisa
45.86%
As redes de comunicação por internet são um sistema e uma forma de organização que têm introduzido e modificado padrões de produção preexistentes em espaços de todo o mundo. Este estudo teve o objetivo de analisar as bases materiais e sociais que trouxeram a internet à sua organização atual no território brasileiro, bem como contribuir teoricamente para a relação entre espaço e interações sociais, por meio da aquisição de conhecimento dos objetos que compõem a internet enquanto um conjunto sociotecnico. Apresentamos os conceitos de rede e território em Geografia, bem como suas relações com comunicação, informação e espaço, em referência a autores que têm em comum a abordagem espacial com relevo nos fenômenos sociais engendrados pela comunicação à distância, especialmente Boris Beaude (2008). Sob as categorias de análise formação socioespacial e território usado de Milton Santos (2002), propomos uma periodização da internet no Brasil e caracterizamos a distribuição espacial das redes e acessos à internet no território no período mais recente. Para o aprofundamento da análise espacial, nos apoiamos teoricamente em Jacques Lévy (2003) para o estudo da internet enquanto um fenômeno eminentemente urbano...

Monitoramento de hosts em redes tcp/ip sobre base georreferenciada com métricas de qualidade

Spozito, Daniel Saverio
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 147 f. : il.
Português
Relevância na Pesquisa
45.8%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia Elétrica - FEIS; Com a globalização e a evolução tecnológica, a capilaridade das instituições, sejam elas públicas ou privadas, é realidade irreversível. O uso de computadores cada vez mais velozes e com elevada capacidade de armazenamento possibilitou a centralização das informações. Nesse contexto, surge a necessidade de interligar os sistemas computacionais com o objetivo de trocar informações, independentemente da região geográfica. A Internet, utilizando tecnologias de redes de dados, com arquitetura projetada para suportar em nível mundial a comunicação entre computadores, passa a ser a principal ferramenta utilizada na interligação de locais geograficamente distribuídos. Com a tecnologia e infraestrutura disponível para efetivar a comunicação, surge também a necessidade de garantir que os sistemas estejam ativos o maior tempo possível, atendendo a desempenho compatível às atividades desenvolvidas, pois as instituições passam a depender da interação entre os sistemas computacionais, independente do ponto do planeta em que estejam. Este trabalho propõe modelar, desenvolver e realizar ensaios de uma ferramenta que auxilie no monitoramento de pontos interligados por redes de comunicação dados sobre protocolo TCP/IP distribuídos geograficamente. O modelo consiste em monitorar um ou mais pontos...

Local Data Communications Network for the Wilford Hall USAF Medical Center

Jackson, Thames F.; Workman, Billy J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 05/11/1980 Português
Relevância na Pesquisa
45.81%
Data Communication technology has progressed to the point that dissimilar computer systems conforming to a common communications protocol can effectively communicate with each other. Until recently this technology has been used in networks that cover a large geographic area. The requirement for local networks is currently coming into focus. Data automation support for the Wilford Hall USAF Medical Center (WHMC) will be provided by off-the-shelf systems under the Tri-Service Medical Information System (TRIMIS) program. A local network (cable bus) is one way to effectively interface these dissimilar computer systems. The MITRI Corporation is functioning as systems engineer to install a cable bus at WHMC. The need for local data communication networks is increasing, and the cable bus offers a potentially effective method to interface multiple dissimilar computers on a cost effective basis.

Country-wide rainfall maps from cellular communication networks

Overeem, Aart; Leijnse, Hidde; Uijlenhoet, Remko
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.82%
Accurate and timely surface precipitation measurements are crucial for water resources management, agriculture, weather prediction, climate research, as well as ground validation of satellite-based precipitation estimates. However, the majority of the land surface of the earth lacks such data, and in many parts of the world the density of surface precipitation gauging networks is even rapidly declining. This development can potentially be counteracted by using received signal level data from the enormous number of microwave links used worldwide in commercial cellular communication networks. Along such links, radio signals propagate from a transmitting antenna at one base station to a receiving antenna at another base station. Rain-induced attenuation and, subsequently, path-averaged rainfall intensity can be retrieved from the signal’s attenuation between transmitter and receiver. Here, we show how one such a network can be used to retrieve the space–time dynamics of rainfall for an entire country (The Netherlands, ∼35,500 km2), based on an unprecedented number of links (∼2,400) and a rainfall retrieval algorithm that can be applied in real time. This demonstrates the potential of such networks for real-time rainfall monitoring...

Multiaccess and fading in communication networks

Yeh, Edmund Meng, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 163 p.; 771750 bytes; 771450 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
45.86%
Two fundamental issues in the design of wireless communication networks are the interference among multiple users and the time-varying nature of the fading wireless channel. We apply fundamental techniques in information theory and queueing theory to gain insights into the structure of these problems. In a terrestrial cellular or space network, multi-user interference arises naturally as different users in the same cell or region attempt to transmit to the base station or satellite at the same time and in the same frequency range. We first examine the impact of this interference on the design of error correction codes for reliable data transmission. At the physical layer of the wireless network, the phenomenon of multi-user interference is captured by the multiaccess (many-to-one) channel model. The set of all data rates at which reliable communication can take place over this channel is characterized via information theory by the so-called multiaccess capacity region. A basic problem is developing coding schemes of relatively low complexity to achieve all rates in this capacity region. By exploiting the underlying geometrical structure of the capacity region, we develop a method of reducing the multi-user coding problem to a set of single-user coding problems using the ideas of time-sharing and successive decoding. Next...

Algoritmo de roteamento bio-inspirado aplicado as redes emergenciais

Fonte: Universidade Federal de Lavras Publicador: Universidade Federal de Lavras
Tipo: Trabalho de Conclusão de Curso
Português
Relevância na Pesquisa
45.8%
In natural disasters, the network infrastructures are often damaged and therefore is extremely necessary that data communication networks be efficient among those people involved in the disaster in order to minimize their loss. The mobile ad hoc networks (MANET) are formed by devices that have wireless communication interfaces, such as PDAs and smartphones. These mobile networks, along with wireless devices used by rescue teams are called emergency networks. The emergency networks have mobility and offer large coverage area. The goal of this work is to make a comparison between Delay Tolerant Networks (DTN) algorithms. The routing algorithms evaluated were epidemic, PRoPHET and the bio-inspired algorithm that comes from the nature of ant colonies. Thus, it could be verified and analysed these three algorithms, and the gotten results showed that the ant colony algorithm based on pheromony is more efficient than both epidemic and PRoPHET.

Data Delivery in Delay Tolerant Networks

M. H. MASSRI, KHALIL
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
45.84%
Current Internet and mobile ad hoc protocols do not properly handle the delivery of data in networks with intermittent connectivity due to link instability. Such networks where nodes are characterized by opportunistic connectivity are referred to as Delay Tolerant Networks (DTNs). Delay tolerant networking is a networking paradigm that deals with the establishment of communication between two nodes when the connectivity is intermittent and/or subject to disruptions and thus a path connecting source and destination cannot be maintained over time. As a consequence, end-to-end latency cannot be guaranteed. A typical example of DTN are vehicular Ad Hoc networks, where a vehicle can send a message to the intended destination only when they are close, or by means of intermediate vehicles carrying a copy of the message. Other examples are military communications in the battlefield, deep space communications and wireless sensor networks. DTNs have been one of the growing topics of interest characterized by significant amount of research efforts invested in this area over the past decade. Routing is one of the major components significantly affecting the overall performance of DTNs in terms of resource consumption, delivery ratio and latency. Data delivery in DTNs mainly rely on the mobility of nodes...

Emergency Communication

Shaw, Rajib; Peary, Brett; Ideta, Ai; Takeuchi, Yukiko
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
45.87%
The Great East Japan Earthquake (GEJE) caused immense damage and congestion in telephone infrastructure, including 1.9 million fixed-line services and 29,000 mobile phone base stations. Government radio communication infrastructure was also seriously damaged. Voice messages were widely used to confirm whether family members and relatives were safe, and satellite phones played a crucial role in emergency communication during the response stage. Social media was extensively used for search and rescue, as well as for fundraising. Social media and community radio reach two distinct age groups: social media for the younger generation and community radio for the older generation. Communication infrastructure is indispensable in securing government functions and protecting lives and property during disasters. Communication systems are used to disseminate warnings to the public, to enable search and rescue organizations to communicate among themselves, and to confirm the safety of family members and relatives. Community radios can provide local information such as times and locations where emergency water and food supplies or relief goods will be delivered.

Assessing the Impact of Communication Costs on International Trade

Fink, Carsten; Mattoo, Aaditya; Neagu, Ileana Cristina
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
45.82%
Recent research suggests that trade costs influence the pattern of specialization and trade, but there is limited empirical research on the determinants of trade costs. The existing literature identifies a range of barriers that separate nations, but then typically focuses only on transport costs. Although communication costs figure prominently in intuitive explanations and casual observations, they have played little role in the formal analysis of trade costs. The authors seek to examine whether this neglect matters, and whether the inclusion of the magnitude and variation of communication costs across partner countries can add value to existing explanations of the pattern of trade. The authors develop a simple multi-sector model of "impeded" trade that generates hypotheses in a gravity-type estimation framework. The main proxies for bilateral communication costs are the per-minute country-to-country calling prices charged in the importing and exporting countries. The use of bilateral variations in prices yields estimates that are superior to the ones obtained from country-specific measures of communication infrastructure used in previous studies. The authors find that international variations in communication costs have a significant influence on bilateral trade flows...

Efficient data transport in wireless sensor networks.

Zhang, Haibo
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009 Português
Relevância na Pesquisa
45.87%
Providing efficient data transport is one of the uppermost objectives in the design of wireless sensor networks (WSNs) since the primary role for each sensor is to report the sensed data to the data sink(s). This thesis focuses on designing efficient data transport schemes for WSNs in the dimensions of energy consumption and time respectively. The developed schemes can be directly applied in a number of applications such as intrusion detection, target tracking, environment monitoring, etc., and can be further extended to underwater acoustic sensor networks and unmanned aerial vehicles (UAVs) networks. With the development of WSN technologies, new challenging research problems such as real-time streaming data gathering and intelligent data communication are emerging. This thesis provides useful foundation for designing next-generation data transport schemes for WSNs. Energy is the most important resource in WSNs because sensor nodes are commonly powered by small batteries, and energy is directly related to the lifetime of nodes and the network. In this thesis, energy-efficient data transport schemes are designed for two major types of WSNs: event-driven sensor networks and time-driven sensor networks. A novel on-line routing scheme called EBGR (Energy-efficient Beaconless Geographic Routing) is designed for event-driven sensor networks characterized by dynamic network topology. The main advantage of EBGR is that it can provide energy-efficient sensor-to-sink routing without any prior neighborhood knowledge. Moreover...

Binational Social Networks and Assimilation: A Test of the Importance of Transnationalism

Mouw, Ted; Chavez, Sergio; Edelblute, Heather; Verdery, Ashton
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Journal article; Text; publisher version
Português
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45.86%
While the concept of transnationalism has gained widespread popularity among scholars as a way to describe immigrants' long-term maintenance of cross-border ties to their origin communities, critics have argued that the overall proportion of immigrants who engage in transnational behavior is low and that, as a result, transnationalism has little sustained effect on the process of immigrant adaptation and assimilation. In this article, we argue that a key shortcoming in the current empirical debate on transnationalism is the lack of data on the social networks that connect migrants to each other and to nonmigrants in communities of origin. To address this shortcoming, our analysis uses unique binational data on the social network connecting an immigrant sending community in Guanajuato, Mexico, to two destination areas in the United States. We test for the effect of respondents' positions in cross-border networks on their migration intentions and attitudes towards the United States using data on the opinions of their peers, their participation in cross-border and local communication networks, and their structural position in the network. The results indicate qualified empirical support for a network-based model of transnationalism; in the U.S. sample we find evidence of network clustering consistent with peer effects...

Strategic Communication for Development Projects : A Toolkit for Task Team Leaders; Comunicacion estrategica para proyectos de desarrollo : herramientas para coordinadores de equipos de trabajo

Cabanero-Verzosa, Cecilia
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
Português
Relevância na Pesquisa
45.83%
Efforts to promote general awareness of public health issues - the traditional goal of information, education, and communication (IEC) programs have built a good foundation for population, health, and nutrition (PHN) activities. So communication programs must be designed to support behavior change in key constituencies delivering the message not just to potential clients, but to health providers as well. This document accompanies a toolkit designed to help Bank task managers plan and supervise the implementation of communication activities in PHN projects. It reviews the basic principles of communication for behavior change, presenting a step-by-stop guide to planning and implementing communication activities and linking those steps to the Bank's project cycle. The toolkit contains a set of practical modules, including: communication research approaches for bank projects; a guide to communication indicators; sample term of reference for Bank and Borrower consultants; guide questions for assessing organizational capacity; sample budget and implementation plan; and case studies of best practice in behavior change communication.

Capturing Technology for Development : An Evaluation of World Bank Group Activities in Information and Communication Technologies, Volume 1. The Evaluation

Independent Evaluation Group
Fonte: Washington, DC: World Bank Publicador: Washington, DC: World Bank
Tipo: Publications & Research :: Publication; Publications & Research :: Publication
Português
Relevância na Pesquisa
45.8%
Technological innovation drives economic progress. Information and communication technologies (ICT) can be leveraged for development, but harnessing this potential depends on an enabling environment for their production, diffusion, and use. Otherwise, technology can widen rather than narrow existing inequalities. Over the past decade developing countries have seen rapid but uneven growth in ICT access and use. The unprecedented spread of mobile technologies, driven by private sector investment and supported by reforms to promote competition, enabled the growth of phone services for the underserved and poor to levels unseen before. But outside mobile telephony, large gaps exist in high-speed Internet access and broadband connectivity and in the diffusion and use of ICT in business, services, and government the areas where ICT can deliver the largest developmental impacts. The World Bank Group's strategy has sought development results in ICT by promoting (i) sector reform, (ii) access to information infrastructure...

Connecting Sub-Saharan Africa : A World Bank Group Strategy for Information and Communication Technology Sector Development

Guislain, Pierre; Ampah, Mavis A.; Besançon, Laurent; Niang, Cécile; Sérot, Alexandre
Fonte: Washington, DC: World Bank Publicador: Washington, DC: World Bank
Tipo: Publications & Research :: Publication; Publications & Research :: Publication
Português
Relevância na Pesquisa
45.8%
The strategy builds on the earlier reform agenda in the sector by leveraging the achievements to date of Sub-Saharan African countries to advance the essential goal of increasing the continent's connectivity. It provides strategies for developing and enhancing the capacity of Africa's information and communication technology sector (ICT) institutions-including regulators, ministries, and regional bodies-to lead the development of an interconnected region and implement sustainable regional strategies for integration and knowledge sharing. Of particular concern is the ability to bring rural areas into the national, regional, and global economies, thus creating new opportunities for the world's poorest citizens.

Online Multicasting for Network Capacity Maximization in Energy-Constrained Ad Hoc Networks

Liang, Weifa; Guo, Xiaoxing
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.86%
In this paper, we present new algorithms for online multicast routing in ad hoc networks where nodes are energy-constrained. The objective is to maximize the total amount of multicast message data routed successfully over the network without any knowledge

Temporal motifs reveal homophily, gender-specific patterns and group talk in mobile communication networks

Kovanen, Lauri; Kaski, Kimmo; Kertész, János; Saramäki, Jari
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/02/2013 Português
Relevância na Pesquisa
45.81%
Electronic communication records provide detailed information about temporal aspects of human interaction. Previous studies have shown that individuals' communication patterns have complex temporal structure, and that this structure has system-wide effects. In this paper we use mobile phone records to show that interaction patterns involving multiple individuals have non-trivial temporal structure that cannot be deduced from a network presentation where only interaction frequencies are taken into account. We apply a recently introduced method, temporal motifs, to identify interaction patterns in a temporal network where nodes have additional attributes such as gender and age. We then develop a null model that allows identifying differences between various types of nodes so that these differences are independent of the network based on interaction frequencies. We find gender-related differences in communication patters, and show the existence of temporal homophily, the tendency of similar individuals to participate in interaction patterns beyond what would be expected on the basis of the network structure alone. We also show that temporal patterns differ between dense and sparse parts of the network. Because this result is independent of edge weights...

Structural differences between open and direct communication in an online community

Karimi, Fariba; Ramenzoni, Verónica C.; Holme, Petter
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/07/2014 Português
Relevância na Pesquisa
45.86%
Most research of online communication focuses on modes of communication that are either open (like forums, bulletin boards, Twitter, etc.) or direct (like e-mails). In this work, we study a dataset that has both types of communication channels. We relate our findings to theories of social organization and human dynamics. The data comprises 36,492 users of a movie discussion community. Our results show that there are differences in the way users communicate in the two channels that are reflected in the shape of degree- and interevent time distributions. The open communication that is designed to facilitate conversations with any member, shows a broader degree distribution and more of the triangles in the network are primarily formed in this mode of communication. The direct channel is presumably preferred by closer communication and the response time in dialogues is shorter. On a more coarse-grained level, there are common patterns in the two networks. The differences and overlaps between communication networks, thus, provide a unique window into how social and structural aspects of communication establish and evolve.

Communication dynamics in finite capacity social networks

Haerter, Jan O.; Jamtveit, Bjorn; Mathiesen, Joachim
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/09/2012 Português
Relevância na Pesquisa
45.85%
In communication networks structure and dynamics are tightly coupled. The structure controls the flow of information and is itself shaped by the dynamical process of information exchanged between nodes. In order to reconcile structure and dynamics, a generic model, based on the local interaction between nodes, is considered for the communication in large social networks. In agreement with data from a large human organization, we show that the flow is non-Markovian and controlled by the temporal limitations of individuals. We confirm the versatility of our model by predicting simultaneously the degree-dependent node activity, the balance between information input and output of nodes and the degree distribution. Finally, we quantify the limitations to network analysis when it is based on data sampled over a finite period of time.; Comment: Physical Review Letter, accepted (5 pages, 4 figures)

Unified communications: The search for ROI through tomorrow’s business communication solutions

Puglia, Vincent
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
45.85%
The traditional workplace is evolving; the way in which businesses communicate today is different than it was in the past and yet is likely to change again in the future. The current state of the economy and globalization has forced every organization to review its future business plans and cut costs everywhere including communications. Organizations are seeking out technology in hopes of finding new ways to reduce their bottom-line communication costs. Today, many enterprise business infrastructures are comprised of separate networks - voice, data, and mobile - yet most of the time these networks never interact. The ability to link business applications from various networks with communications proves to be valuable and is known as convergence. Convergence is defined as the combining of one or more elements into one. Unified Communications is a concept that looks to build on convergence, although it is not a new technology. Unified Communications is the term coined by the communications industry that signifies the comprehensive integration of various communication networks for reasons of increased revenue and reduced costs. Unified Communications will fundamentally transform the way in which people work - from decreased carrier costs to increased response times...