792 resultados para Peer-to-Peer networks
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La implementación de indicaciones geográficas, generan distintos efectos socio-económicos, tecnológicos y ambientales, no sólo a nivel de los productores directamente involucrados, sino también en el marco del sistema agroalimentario local (SIAL). Entre estos últimos, se destaca la organización colectiva de los productores y el desarrollo de una gobernanza, a partir del conjunto de actividades desarrolladas por el Consejo Regulador (CR), en torno al control de calidad y la promoción del producto. El concepto de gobernanza territorial implica llevar a cabo procesos de organización colectiva en red en los que tienen lugar procesos de coordinación multi-nivel entre los agentes, las empresas y las instituciones locales, en un contexto de asimetría en la información y de la existencia de numerosos decisores. El objetivo de esta Tesis Doctoral es realizar un aporte metodológico para el estudio de la gobernanza territorial en sistemas agroalimentarios localizados, a partir de la construcción de indicadores (de calidad, innovación, efectos económicos y prácticas ambientales) y el análisis de las redes de colaboración en materia de difusión del conocimiento e innovaciones técnicas, organizativas y comerciales en la Comarca de Sierra Mágina. Para responder el objetivo se aplica análisis de redes sociales y se construyen indicadores sintéticos para valorizar los efectos. Se realizan encuestas a la totalidad de almazaras presentes en la Comarca de Sierra Mágina, tanto a las que poseen el signo de calidad como a las que no cuentan con dicha marca territorial y entrevistas a testigos privilegiados. En las mismas se consulta sobre las actividades y proyectos que realizan en forma conjunta con otras almazaras e instituciones, así como los actores o referentes a quiénes consultan en temas relacionados con la calidad en la producción olivícola y la obtención de aceite, así como aquellos actores a quienes consultan en aspectos referidos a la Comercialización y gestión. A partir de la información recabada, se obtienen cuatro indicadores sintéticos de efectos de la implantación de una DOP en las almazaras adheridas, referidos a la adopción de innovaciones productivas y organizativas, a la calidad en producto y procesos, a las rentas de diferenciación y a las prácticas ambientales. Asimismo se generan las matrices bi-narias y valuadas para las redes de colaboración en la difusión del conocimiento y se calculan los indicadores particulares. Esto nos permite estudiar las características de las redes que se generan (tamaño, conectividad), el papel del CR en la gobernanza territorial y de otras instituciones del medio, así como identificar actores centrales y grupos en el proceso de difusión de conocimientos. Los resultados muestran que los SIAL pueden beneficiarse de la organización interprofesional y de cooperación interinstitucional a escala local que se producen tras la implantación de una DOP. Se desarrolla un proceso de articulación y un fuerte intercambio de conocimientos entre actores ligados al propio proceso de control de la calidad diferencial. Pero, junto con ello, se desarrollan actividades de formación y de promoción del patrimonio comarcal y se consolidan redes locales de innovación y colaboración mutua en distintas actividades, tanto entre actores de la propia cadena de producción, como entre éstos y las instituciones del medio. Estas actividades, junto con la presencia de un entramado institucional denso, permiten el desarrollo de una gobernanza territorial alrededor del sistema agroalimentario del aceite de oliva. ABSTRACT The implementation of geographical indications has different socio-economic, technological and environmental effects not only for the producers involved but also for the local agro food system (LAFS). Among the latter, we can highlight the collective organization of producers and the development of territorial governance through a series of tasks developed by the Regulatory Board (RB) as regards quality control and product marketing. The concept of territorial governance involves processes of collective organization in networks, where processes of multi-level coordination among agents, enterprises and local institutions take place within a context of asymmetry of information and numerous decision makers. The objective of this Doctoral Thesis is to contribute with methodological tools for the study of territorial governance in local agro food systems by constructing indicators (of quality, innovation, economic effects and environmental practices) and by analyzing networks of collaboration in terms of dissemination of technical, organizational and commercial innovation and knowledge in Comarca de Sierra Mágina. To achieve that objective, social network analysis is applied and synthetic indicators are elaborated to valorize the effects. Interviews to key actors and surveys to every oil mill in Comarca de Sierra Mágina are carried out, not only in those oil mills that host a label of quality but also in the ones that do not hold it. These interviews inquire about tasks and projects performed together with other oil mills and institutions and about actors or referents consulted in topics related to quality in olive production and oil extraction as well as in management and marketing. From all the information collected, four synthetic indicators of the effects of establishing Protected Designations of Origen (PDOs) in the associate oil mills are obtained, in terms of adoption of productive and organizational innovations, process and product quality, income differentiation and environmental practices. In the same way, binary and valorized matrixes are generated for those networks collaborating in the dissemination of knowledge and specific indicators are calculated. This allows to study networks (size, connectivity), the role of RB in territorial governance and other institutions involved and to identify main actors and groups in the process of knowledge dissemination. The results show that the LAFS can benefit from inter-professional organizations and inter- institutional cooperation at local levels by implementing PDOs. A process of articulation and strong exchange of knowledge is developed among those actors involved in controlling differential quality. But, at the same time, activities for the formation and promotion of the “comarca” patrimony are developed and local networks of innovation and mutual collaboration are built for different activities, not only among actors in the production process itself, but between these actors and local institutions as well. These tasks, together with the existence of a dense spatial entrepreneurial network, allow the development of territorial governance on the olive oil agro food system.
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The Biomolecular Interaction Network Database (BIND; http://binddb.org) is a database designed to store full descriptions of interactions, molecular complexes and pathways. Development of the BIND 2.0 data model has led to the incorporation of virtually all components of molecular mechanisms including interactions between any two molecules composed of proteins, nucleic acids and small molecules. Chemical reactions, photochemical activation and conformational changes can also be described. Everything from small molecule biochemistry to signal transduction is abstracted in such a way that graph theory methods may be applied for data mining. The database can be used to study networks of interactions, to map pathways across taxonomic branches and to generate information for kinetic simulations. BIND anticipates the coming large influx of interaction information from high-throughput proteomics efforts including detailed information about post-translational modifications from mass spectrometry. Version 2.0 of the BIND data model is discussed as well as implementation, content and the open nature of the BIND project. The BIND data specification is available as ASN.1 and XML DTD.
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Com o escopo de fornecer subsídios para compreender como o processo de colaboração científica ocorre e se desenvolve em uma instituição de pesquisas, particularmente o IPEN, o trabalho utilizou duas abordagens metodológicas. A primeira utilizou a técnica de análise de redes sociais (ARS) para mapear as redes de colaboração científica em P&D do IPEN. Os dados utilizados na ARS foram extraídos da base de dados digitais de publicações técnico-científicas do IPEN, com o auxílio de um programa computacional, e basearam-se em coautoria compreendendo o período de 2001 a 2010. Esses dados foram agrupados em intervalos consecutivos de dois anos gerando cinco redes bienais. Essa primeira abordagem revelou várias características estruturais relacionadas às redes de colaboração, destacando-se os autores mais proeminentes, distribuição dos componentes, densidade, boundary spanners e aspectos relacionados à distância e agrupamento para definir um estado de redes mundo pequeno (small world). A segunda utilizou o método dos mínimos quadrados parciais, uma variante da técnica de modelagem por equações estruturais, para avaliar e testar um modelo conceitual, apoiado em fatores pessoais, sociais, culturais e circunstanciais, para identificar aqueles que melhor explicam a propensão de um autor do IPEN em estabelecer vínculos de colaboração em ambientes de P&D. A partir do modelo consolidado, avaliou-se o quanto ele explica a posição estrutural que um autor ocupa na rede com base em indicadores de ARS. Nesta segunda parte, os dados foram coletados por meio de uma pesquisa de levantamento com a utilização de um questionário. Os resultados mostraram que o modelo explica aproximadamente 41% da propensão de um autor do IPEN em colaborar com outros autores e em relação à posição estrutural de um autor na rede o poder de explicação variou entre 3% e 3,6%. Outros resultados mostraram que a colaboração entre autores do IPEN tem uma correlação positiva com intensidade moderada com a produtividade, da mesma forma que, os autores mais centrais na rede tendem a ampliar a sua visibilidade. Por fim, vários outros indicadores estatísticos bibliométricos referentes à rede de colaboração em P&D do IPEN foram determinados e revelados, como, a média de autores por publicação, média de publicações por autores do IPEN, total de publicações, total de autores e não autores do IPEN, entre outros. Com isso, esse trabalho fornece uma contribuição teórica e empírica aos estudos relacionados à colaboração científica e ao processo de transferência e preservação de conhecimento, assim como, vários subsídios que contribuem para o contexto de tomada de decisão em ambientes de P&D.
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O objetivo geral deste estudo foi analisar a relação entre a rede e apoio social, satisfação com o apoio social recebido e as variáveis sociodemográficas, de saúde física e mental, dos idosos atendidos em um Ambulatório de Geriatria de um Hospital Geral Terciário do interior paulista. Trata-se de um estudo descritivo, transversal e exploratório, realizado com 98 idosos atendidos no referido ambulatório. Para a coleta de dados, utilizaram-se o Mini Exame do Estado Mental, um questionário de caracterização sociodemográfica e de saúde, a Escala de Depressão Geriátrica (EDG-15), o Índice de Katz, a Escala de Lawton e Brody, a Escala de medida da rede e apoio social do Medical Outcomes Study e a Escala de Satisfação com o Suporte Social. Os aspectos éticos foram respeitados conforme a Resolução 466/2012 do Conselho Nacional de Saúde. A média de idade dos idosos foi de 80,1 anos, 70,4% eram mulheres, 49,0% viúvos; a média de anos de estudo foi 2,3; 24,5% dos idosos residiam com o cônjuge e filhos ou somente com os filhos; a renda familiar média foi de R$1.773,70. Quanto à capacidade funcional, 80,6% eram independentes para as atividades básicas da vida diária e 88,8% eram parcialmente dependentes para as instrumentais. Os idosos possuíam, em média, 5,3 diagnósticos médicos e os sintomas depressivos estiveram presentes para 61,2% deles. Quanto à rede social, o escore total médio foi de 6,4 pessoas para contato na rede, sendo que 36,7% apresentavam médio contato e participação em atividades sociais. Em relação ao apoio social, o maior escore médio foi para a dimensão material (90,2) e o menor para a interação social positiva (81,8); já para a satisfação com o suporte social, 36,7% e 32,7% apresentaram alta e média satisfação, respectivamente. Foi encontrada correlação inversa entre os escores de todas as dimensões da escala de apoio social e os escores da EDG-15, indicando que quanto maior o apoio social em todas as dimensões, menor é a presença de sintomas depressivos e houve diferenças estatisticamente significativas para todas as dimensões, material (p=0,014), afetiva (p=0,026), interação (p=0,011), emocional (p=0,001) e informação (p=0,005); já a correlação entre os escores das dimensões da escala de apoio social e os escores na escala de Lawton e Brody, foi inversa e fraca para as dimensões material (r=-0,157) e informação (r=-0,027), sugerindo que quanto menor a independência para as AIVDs, maior o apoio social nas referidas dimensões, porém, não houve diferença estatisticamente significativa, material (p=0,121) e informação (p=0,789). A correlação entre os escores da EDG-15 e os escores da escala de satisfação com o apoio social, foi inversa e moderada (r=- 0,467), indicando que quanto maior a satisfação com o apoio social, menor a presença de sintomas depressivos, sendo estatisticamente significativa (p=0,000). Evidencia-se a importância de conhecer se os idosos estão inseridos em rede social e se percebem o apoio social para um melhor direcionamento da assistência prestada ao idoso e para o planejamento e formulação de políticas públicas, programas e projetos voltados a essa população
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This article considers an empirical approach to the relationships among three well known concepts: “Benevolence” (Schwartz), Solidarity and Resilience ("Subjective wellbeing scale" - SWB). The first concept refers to cultural values, the second one to social networks and the third to the ability to recover from crisis. The measurement of solidarity has been done from the point of view of supportive ties. The baseline hypothesis considers that the presence of a high value in Benevolence contributes to the involvements in solidarity networks. Participation in supportive relationships facilitates recovery from personal crisis. Using data from the European Social Survey (ESS6), we conclude from this structural analysis that the resilience reflected in a society is partly a consequence of the supportive networks shaped by the presence of benevolence values.
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Thesis (Master's)--University of Washington, 2016-06
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Ecosystems and the species and communities within them are highly complex systems that defy predictions with any degree of certainty. Managing and conserving these systems in the face of uncertainty remains a daunting challenge, particularly with respect to developing networks of marine reserves. Here we review several modelling frameworks that explicitly acknowledge and incorporate uncertainty, and then use these methods to evaluate reserve spacing rules given increasing levels of uncertainty about larval dispersal distances. Our approach finds similar spacing rules as have been proposed elsewhere - roughly 20-200 km - but highlights several advantages provided by uncertainty modelling over more traditional approaches to developing these estimates. In particular, we argue that uncertainty modelling can allow for (1) an evaluation of the risk associated with any decision based on the assumed uncertainty; (2) a method for quantifying the costs and benefits of reducing uncertainty; and (3) a useful tool for communicating to stakeholders the challenges in managing highly uncertain systems. We also argue that incorporating rather than avoiding uncertainty will increase the chances of successfully achieving conservation and management goals.
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Data on the occurrence of species are widely used to inform the design of reserve networks. These data contain commission errors (when a species is mistakenly thought to be present) and omission errors (when a species is mistakenly thought to be absent), and the rates of the two types of error are inversely related. Point locality data can minimize commission errors, but those obtained from museum collections are generally sparse, suffer from substantial spatial bias and contain large omission errors. Geographic ranges generate large commission errors because they assume homogenous species distributions. Predicted distribution data make explicit inferences on species occurrence and their commission and omission errors depend on model structure, on the omission of variables that determine species distribution and on data resolution. Omission errors lead to identifying networks of areas for conservation action that are smaller than required and centred on known species occurrences, thus affecting the comprehensiveness, representativeness and efficiency of selected areas. Commission errors lead to selecting areas not relevant to conservation, thus affecting the representativeness and adequacy of reserve networks. Conservation plans should include an estimation of commission and omission errors in underlying species data and explicitly use this information to influence conservation planning outcomes.
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Currently, wireless technology is revolutionizing the way we share information and communicate. The demands for mobility have made wireless technology the primary source for voice communication. Code-division multiple-access (CDMA) is a very popular spread spectrum application due to its claims of low transmission power, higher system capacity, ability to mitigate multipath fading and user interference. In that case, frequency-hopping code-division multiple access (FH-CDMA) has received considerable attention over the past few years. This technique will allow a better performance over a fading channel, message privacy, and immunity to narrowband interference. This paper addresses the characteristics of FH-CDMA in WPAN networks, with an emphasis on frequency-hopped Bluetooth systems. A performance evaluation of FH-CDMA is discussed and simulated. The analysis shows the interaction between the designed parameters and their effect on the network system. Most specifically, the FH-CDMA scheme provides frequency and temporal diversity to combat the effects of interference.
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A simple method for training the dynamical behavior of a neural network is derived. It is applicable to any training problem in discrete-time networks with arbitrary feedback. The method resembles back-propagation in that it is a least-squares, gradient-based optimization method, but the optimization is carried out in the hidden part of state space instead of weight space. A straightforward adaptation of this method to feedforward networks offers an alternative to training by conventional back-propagation. Computational results are presented for simple dynamical training problems, with varied success. The failures appear to arise when the method converges to a chaotic attractor. A patch-up for this problem is proposed. The patch-up involves a technique for implementing inequality constraints which may be of interest in its own right.
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The main aim of this article is to shed some light on the way in which actor network theory (ANT) might contribute to case research in accounting. The paper will seek to explain some of the theoretical suppositions which are commonly associated with ANT and which have so far made little impact on the accounting literature. At the same time the accounting literature has shown a particular reluctance to engage with the central concept of ANT which Lee and Hassard characterise as the desire to bring together the "human and non-human, social and technical factors in the same analytical view". The article also features a discussion of a research project which used an approach giving emphasis to both humans and objects in order to understand how ``facts'' have come to be settled as they are. In taking such views into the research it is hoped to provide insight into both the detail of accounting as it is practised within organisations and the manner in which human actors and objects of technology may combine to constitute networks within organisations.
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Distributed network utility maximization (NUM) is receiving increasing interests for cross-layer optimization problems in multihop wireless networks. Traditional distributed NUM algorithms rely heavily on feedback information between different network elements, such as traffic sources and routers. Because of the distinct features of multihop wireless networks such as time-varying channels and dynamic network topology, the feedback information is usually inaccurate, which represents as a major obstacle for distributed NUM application to wireless networks. The questions to be answered include if distributed NUM algorithm can converge with inaccurate feedback and how to design effective distributed NUM algorithm for wireless networks. In this paper, we first use the infinitesimal perturbation analysis technique to provide an unbiased gradient estimation on the aggregate rate of traffic sources at the routers based on locally available information. On the basis of that, we propose a stochastic approximation algorithm to solve the distributed NUM problem with inaccurate feedback. We then prove that the proposed algorithm can converge to the optimum solution of distributed NUM with perfect feedback under certain conditions. The proposed algorithm is applied to the joint rate and media access control problem for wireless networks. Numerical results demonstrate the convergence of the proposed algorithm. © 2013 John Wiley & Sons, Ltd.
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This paper presents an argument that it is possible for an organisation to manage networks, but understanding this involves consideration of what is meant by "managing". Based on prior research and data from a major longitudinal action research study in the health sector, the paper describes six network management roles: network structuring agent; co-ordinator; advisor; information broker; relationship broker; innovation sponsor. The necessary "assets" for effective performance of these roles are identified, in particular those relating to team competence. The findings enrich and significantly develop previous work on network management roles and activities, and their influencing factors. It is concluded that, given the specific nature of the networks studied, further research is required to evaluate the generalisability of the findings, though initial indications are promising.
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In the agri-food industry, Internet-based applications changed the way companies conduct business mainly by facilitating activities that were already taking place, rather by giving birth to virtual networks creation. Due to the specific characteristics of the sector, Internet's huge potential has not been fully exploited yet, still remaining a new communication tool. This paper aims at giving empirical insights regarding the use of Internet-based applications in the agri-food supply chain, by focusing on the Greek fruit canning sector. In particular, the paper identifies companies' perceptions regarding perceived benefits, constrained factors and motivation factors towards the use of Internet-based applications. Results indicate that companies recognise benefits arising from the use of Internet, however they still use traditional ways when communicating with their partners. Regarding transportation issues, while companies' overall satisfaction is rather moderate and differs significantly from the importance placed on a number of criteria, companies are still sceptical in using Electronic Transportation Marketplace. © 2004 Elsevier Ltd. All rights reserved.
Resumo:
Distributed network utility maximization (NUM) is receiving increasing interests for cross-layer optimization problems in multihop wireless networks. Traditional distributed NUM algorithms rely heavily on feedback information between different network elements, such as traffic sources and routers. Because of the distinct features of multihop wireless networks such as time-varying channels and dynamic network topology, the feedback information is usually inaccurate, which represents as a major obstacle for distributed NUM application to wireless networks. The questions to be answered include if distributed NUM algorithm can converge with inaccurate feedback and how to design effective distributed NUM algorithm for wireless networks. In this paper, we first use the infinitesimal perturbation analysis technique to provide an unbiased gradient estimation on the aggregate rate of traffic sources at the routers based on locally available information. On the basis of that, we propose a stochastic approximation algorithm to solve the distributed NUM problem with inaccurate feedback. We then prove that the proposed algorithm can converge to the optimum solution of distributed NUM with perfect feedback under certain conditions. The proposed algorithm is applied to the joint rate and media access control problem for wireless networks. Numerical results demonstrate the convergence of the proposed algorithm. © 2013 John Wiley & Sons, Ltd.