Correspondence between the one-loop three-point vertex and the Y and Delta electric resistor networks

Different mathematical methods have been applied to obtain the analytic result for the massless triangle Feynman diagram yielding a sum of four linearly independent (LI) hypergeometric functions of two variables F-4. This result is not physically acceptable when it is embedded in higher loops, because all four hypergeometric functions in the triangle result have the same region of convergence and further integration means going outside those regions of convergence. We could go outside those regions by using the well-known analytic continuation formulas obeyed by the F-4, but there are at least two ways we can do this. Which is the correct one? Whichever continuation one uses, it reduces a number of F-4 from four to three. This reduction in the number of hypergeometric functions can be understood by taking into account the fundamental physical constraint imposed by the conservation of momenta flowing along the three legs of the diagram. With this, the number of overall LI functions that enter the most general solution must reduce accordingly. It remains to determine which set of three LI solutions needs to be taken. To determine the exact structure and content of the analytic solution for the three-point function that can be embedded in higher loops, we use the analogy that exists between Feynman diagrams and electric circuit networks, in which the electric current flowing in the network plays the role of the momentum flowing in the lines of a Feynman diagram. This analogy is employed to define exactly which three out of the four hypergeometric functions are relevant to the analytic solution for the Feynman diagram. The analogy is built based on the equivalence between electric resistance circuit networks of types Y and Delta in which flows a conserved current. The equivalence is established via the theorem of minimum energy dissipation within circuits having these structures.

Modeling 3-D desiccation soil crack networks using a mesh fragmentation technique

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Typology of companies networks for competitive assessment: an application in higher education institutions

Taking into account the changes in the market scenario by virtue of globalization, Institutes of Higher Education (IES) as well as other organizations seek their competitive stability. For that reason, it is up to organizations to adopt innovative models of management for their operations aimed at improving results. Company networks consist of a model that is perfect for uniting efforts through cooperation among partners in a given business, which can involve ties of different natures. This paper shows the development and the application of an auxiliary technique to analyze the intensity, nature and importance of internal and external relations in the formation of results for a company network. For such, a multiple case study was conducted at two IES in the State of São Paulo and their networks of partners and employees in order to observe their specificities and organizational strategies. The study demonstrated the existence of specific performance criteria (pillars) for each IES and its network, resulting from its competitive reality. It reveals evidence that the education pillar is strengthened in both cases, and the research pillar is growing, although it is the weakest. The outreach pillar is the most robust in the public IES and the financial sustainability pillar is relevant for the private IES, and it was only detected in this IES.

Artificial immune networks Copt-aiNet and Opt-aiNet applied to the reconfiguration problem of radial electrical distribution systems

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Social networks on the Internet: a practical investigation about file sharing on Facebook

The social networks on the internet have experienced rapid growth and joined millions of users in Brazil and throughout the world. Such networks allow groups of people to communicate and exchange information. Sharing information in files is also a growing activity on the internet and is done in various ways. However, applications are not yet available to enable file sharing on Facebook, the premier social network today. This study aims to investigate how users use Facebook, and their practices for file sharing. Due to the experimental nature of this research, we opted for a data collection survey, applied over the web. From the data analysis, we have found a frequent use of file sharing, but no interest in paid services. As for Facebook, there was an extensive use of applications. The set of results shows a favourable scenario for applications that allow file sharing on Facebook.

An analysis of embeddedness in the value creation in interorganisational networks: an illustrative example in Brazil

The purpose of this article is to propose a methodological approach to analyse how the positioning of actors in an interorganisational network can influence the elements of value creation. This study fills a gap in the existing literature by exploring the relationship between the positioning of actors and the value creation in a context of interorganisational networks. The case study method was employed and the data was obtained from four companies of an interorganisational network, located in Brazil, which produces earthmoving equipments. The central actor in this network is benefited through access to resources, power and information of the other network actors. The centrality position seems to help this company in the absorption and diffusion of knowledge among the other network actors. The research indicates, that a dense core (through strong ties) and redundancy (for triangulation and knowledge absorption), benefited the following value creation elements: tangible; intangible; services and economic.