Divisão de Observação da Terra e Geoinformática

Essa página está em modo somente de leitura. Você pode visualizar a fonte, mas não alterá-la. Informe-se com o administrador do Wiki, caso você ache que isso está incorreto.
====== Networks ======

=====Journals=====

  * [[http://www.elsevier.com/wps/find/journaldescription.cws_home/505596/description#description|Social Networks]]


=====Terminology=====

  * **rank-based friendship:** a connection between two agents, where the probability that person u befriends person v is inversely proportional to the number of people who are closer to u than v is.
  * **small world experiment:** several experiments conducted by Stanley Milgram examining the average path length for social networks of people in the United States. The research was groundbreaking in that it revealed that human society is a small world type network characterized by shorter-than-expected path lengths.
  * **six degrees of separation:** the term coined after the mean distance between two persons in the small world experiment was six.
  * **Erdős number:** is a way of describing the "collaborative distance", in regard to mathematical papers, between an author and Paul Erdős, one of the most prolific writers of mathematical papers.
  * **Dunbar's number:** the typical size of a social network is constrained to about 150 members due to possible limits in the capacity of the human communication channel.
  * **social distance:** the shortest number of steps between 2 persons in a network.
  * **Fruchterman-Reingold algorithm**: Graph Drawing by Force-directed Placement (1991)
  * **Boolean network:** a set of Boolean variables whose state is determined by other variables in the network. They are a particular case of discrete dynamical networks, where time and states are discrete, i.e. they have a bijection onto an integer series. Boolean and elementary cellular automata are particular cases of Boolean networks.

=====Motivation=====

\\

//"O trigo está 227% mais caro hoje do que estava há pouco mais de dois anos, em janeiro de 2006; a soja, no período, subiu 132%, e o milho, 157%. O arroz dobrou de preço em três meses. Os dados são assim impressionantes, e a armadilha na qual o mundo entrou é difícil de desarmar: parte do problema é causada pela mudança climática; parte da solução pode aprofundar a mudança climática".//

[[http://www.correiodabahia.com.br/economia/panoramaeconomico_impressao.asp?codigo=151796|Miriam Leitão]], 17/04/2008.


\\

//"As restrições da União Européia são relacionadas à **rastreabilidade**, ou seja, o monitoramento do trânsito dos bois, do nascimento ao abate. Em novembro do ano passado, algumas fazendas e frigoríficos apresentaram inconformidades que foram relatadas por veterinários da União Européia, em missão oficial"//

[[http://www.agenciabrasil.gov.br/noticias/2008/02/15/materia.2008-02-15.5505352094/view|Agência Brasil]], 15 de Fevereiro de 2008.

\\

{{  http://www.leg.ufpr.br/~pedro/figures/network-infoflow.jpg}}


=====Papers=====

====The Spreading of Rumor====


The evolution of social networks can sometimes be modeled by the use of agent based models, providing insight into the interplay between communication rules, rumor spreading and social structure. Here is an interactive model of rumour spreading, based on rumour spreading from model on [[http://cmol.nbi.dk/models/infoflow/infoflow.html|Cmol]].

Diffusion of innovations theory explores social networks and their role in influencing the spread of new ideas and practices. Change agents and opinion leaders often play major roles in spurring the adoption of innovations, although factors inherent to the innovations also play a role.

Nevertheless, even as an average person may only be able to establish a few strong ties due to possible constraints of human communication channels, Mark Granovetter found in one study that more numerous weak ties can be important in seeking information and innovation. Cliques have a tendency to more homogeneous opinions as well as sharing many common traits. This homophillic tendency was the reason for the members of the cliques to be attracted together in the first place. However, being similar, each member of the clique would also know more or less what the other members knew. To find new information or insights, members of the clique will have to look beyond the clique to its other friends and acquaintances. This is what Granovetter called the "the strength of weak ties".

Guanxi is a central concept in Chinese society (and other East Asian cultures) that can be summarized as the use of personal influence. Guanxi can be studied from a social network approach.[6]

The small world phenomenon is the hypothesis that the chain of social acquaintances required to connect one arbitrary person to another arbitrary person anywhere in the world is generally short. The concept gave rise to the famous phrase six degrees of separation after a 1967 small world experiment by psychologist Stanley Milgram. In Milgram's experiment, a sample of US individuals were asked to reach a particular target person by passing a message along a chain of acquaintances. The average length of successful chains turned out to be about five intermediaries or six separation steps (the majority of chains in that study actually failed to complete). The methods (and ethics as well) of Milgram's experiment was later questioned by an American scholar, and some further research to replicate Milgram's findings had found that the degrees of connection needed could be higher.[7] Academic researchers continue to explore this phenomenon as Internet-based communication technology has supplemented the phone and postal systems available during the times of Milgram. A recent electronic small world experiment at Columbia University found that about five to seven degrees of separation are sufficient for connecting any two people through e-mail.[8]

The study of socio-technical systems is loosely linked to social network analysis, and looks at relations among individuals, institutions, objects and technologies.








====Network Formation and Strategic Firm Behaviour to Explore and Exploit====
|M Özman, 2007| Journal of Artificial Societies and Social Simulation 11(1)| [[http://jasss.soc.surrey.ac.uk/11/1/7.html|html]]|

\\

**Abstract:**    The aim of this paper is to investigate the effect of technological opportunities and knowledge tacitness on inter-firm network formation, under two different industry regimes. In the first regime environment is stable and the aim of firms is to exploit knowledge. In this case, they attribute more value to repeated interactions with geographically close firms. In the second regime, there is environmental turbulence, which increases the value of access to novelties from distant partners for the purpose of exploration. The question addressed is, under these regimes how do technological opportunities and knowledge tacitness influence structure of networks? A simulation model is carried out where firms select partners and learn from them, which further shapes their selection process. How the macro structure of the network is shaped from the individual partner selection decisions of firms is analysed. The results reveal that in both regimes richer technological opportunities and higher tacitness generates local and global star firms depending on the parameter range.

\\

====Scale-free network of a dengue epidemic====
|E Massad, S Ma, M Chen, C J Struchiner, N Stollenwerk, M Aguiar, 2008| Applied Mathematics and Computation 195:376–381| [[http://www.leg.ufpr.br/~pedro/papers/amc/network-dengue.pdf|pdf]]|

\\

**Abstract:** In this work we show that the dengue epidemic in the city of Singapore organized itself into a scale-free network of
transmission as the 2000–2005 outbreaks progressed. This scale-free network of cluster comprised geographical breeding
places for the aedes mosquitoes, acting as super-spreaders nodes in a network of transmission. The geographical organization
of the network was analysed by the corresponding distribution of weekly number of new cases. Therefore, our
hypothesis is that the distribution of dengue cases reflects the geographical organization of a transmission network, which
evolved towards a power law as the epidemic intensity progressed until 2005.

\\


====The Exploration of Technological Diversity and Geographic Localization in Innovation: Start-Up Firms in the Semiconductor Industry====
|1997|Small Business Economics 9(1)21-31|



====The Social Structure of Entrepreneurial Activity: Geographic Concentration of Footwear Production in the United States, 1940–1989====
|O Sorenson and P G Audia, 2000| American Journal of Sociology 106(2) 424–62| [[http://www.journals.uchicago.edu/doi/abs/10.1086/316962?cookieSet=1&journalCode=ajs|html]]|

\\

**Abstract:** Nearly all industries exhibit geographic concentration. Most theories of the location of industry explain the persistence of these production centers as the result of economic efficiency. This article argues instead that heterogeneity in entrepreneurial opportunities, rather than differential performance, maintains geographic concentration. Entrepreneurs need exposure to existing organizations in the industry to acquire tacit knowledge, obtain important social ties, and build self-confidence. Thus, the current geographic distribution of production places important constraints on entrepreneurial activity. Due to these constraints, new foundings tend to reify the existing geographic distribution of production. Empirical evidence from the shoe industry supports this thesis.

\\


====The Exploration of Technological Diversity and Geographic Localization in Innovation: Start-Up Firms in the Semiconductor Industry====
|P Almeida and B Kogut, 1997| Small Business Economics 9(1)21-31|

\\

**Abstract:**  This paper examines the innovative ability of small firms in the semiconductor industry regarding their exploration of technological diversity and their integration within local knowledge networks. Through the analysis of patent data, we compare the innovative activity of start-up firms and larger firms. We find that small firms explore new technological areas by innovating in less lsquocrowdedrsquo areas. The analysis of patent citation data reveals that small firms are tied into regional knowledge networks to a greater extent than large firms. These findings point to the role of entrepreneurial firms in the exploration of new technological spaces and in the diffusion of their accumulated knowledge through local small firm networks.

\\

====Duocentered networks====
|L Coromina, J Guia, G Coenders, A Ferligoj| Social Networks 30 (2008) 49–59|

\\

**Abstract:** When a pair of individuals is central to a research problem (e.g., husband and wife, PhD student and supervisor) the concept of “duocentered” networks can be defined as a useful extension of egocentered networks. This new structure consists of a pair of central egos and their direct links with alters, instead of just one central ego as in the egocentered networks or multiple egos as in complete networks. The key point in this kind of network is that ties exist between the central pair of egos and between them and all alters, but the ties among alters are not considered. Duocentered networks can also be considered as a compromise between egocentered and complete networks. Complete network measurements are often costly to obtain and tend to contain a large proportion of missing data (especially for peripheral actors). Egocentered network data are less costly but a
lot of information is lost with their use when a pair of individuals is the relevant unit of analysis.
From the definition of duocentered networks, we develop new social network measures, some of which based on the measures for complete
networks such as degree, closeness centrality or density, both absolute and relative, while others are tailored to dealing with specific characteristics of the duocentered network structures.
The proposed measures are used in the analysis of the networks of Slovenian PhD students and their supervisors. We specify three regression
models to predict PhD student’s academic performance on the basis of these duocentered network measures for different relations such as advice,
collaboration, emotional support, and trust. The results show that absolute duocentered measures predict performance best. When compared with
egocentered network measures a higher predictive power of duocentered networks is revealed.

\\


====Towards a theory of supply chain management: the constructs and measurements====
|I J Chen and A Paulraj, 2004| Journal of Operations Management 22(2) 119-150|

\\

Rising international cooperation, vertical disintegration, along with a focus on core activities have led to the notion that firms are links in a networked supply chain. This novel perspective has created the challenge of designing and managing a network of interdependent relationships developed and fostered through strategic collaboration. Although research interests in supply chain management (SCM) are growing, no research has been directed towards a systematic development of SCM instruments.

This study identifies and consolidates various supply chain initiatives and factors to develop key SCM constructs conducive to advancing the field. To this end, we analyzed over 400 articles and synthesized the large, fragmented body of work dispersed across many disciplines. The result of this study, through successive stages of measurement analysis and refinement, is a set of reliable, valid, and unidimensional measurements that can be subsequently used in different contexts to refine or extend conceptualization and measurements or to test various theoretical models, paving the way for theory building in SCM.

\\


====A network economic model for supply chain versus supply chain competition====
|D Zhang, 2006| Omega 34(3)283-295|

\\

**Abstract:** We study a supply chain economy (SCE) that comprises heterogeneous SC involving multiple products and competing for multiple markets. The proposed network model is built upon operation links and interface links, representing, respectively, substantial SC operations and coordination functions between the operations. The paper presents a variational inequality formulation of the problem, the solution of which determines the winning SC and their market shares in the equilibrium of SCE. We furnish qualitative properties such as existence and uniqueness of the equilibrium. Numerical examples are presented for illustrative purpose.

\\




====Economic Action and Social Structure: The Problem of Embeddedness====
|M. Granovetter, 1985| American Journal of Sociology 91:481-510| [[http://www.leg.ufpr.br/~pedro/papers/embeddedness-social-structure-granovetter.pdf|pdf]]|

\\

**Abstract:** How behaviour and institutions are affected by social relations is one of the classic
questions of social theory. This paper concerns the extent to which economic action is embedded in
structures of social relations, in modern industrial society. Although the usual neoclassical 
accounts provide an "undersocialized" or atomized-actor explanation of such action, reformist 
economics who attempt to bring social structure back in do so in the "oversocialized" way 
criticized by Dennis Wrong. Under- and over socialized accounts are paradoxically similar in their
neglect of ongoing structures of social relations, and a sophisticated account of economic action 
must consider its embeddedness in such structures. The argument is illustrated by a critic of
Oliver Willamson's "markets and hierarchies" research program.

\\


FIXME Checar a veracidade: the behaviour of individuals cannot be explained except in terms of their 
interaction with other individuals known to them. Individuals being influenced by other individuals
without slavishly imitating them.

====Capturing Social Embeddedness: a constructivist approach====
|B Edmonds, 1999| Adaptive Behaviour 7:323-348| [[http://www.leg.ufpr.br/~pedro/papers/social-embeddedness-constructivist.pdf|pdf]]|

\\

**Abstract:** A constructivist approach is applied to characterising social embeddedness. Social embeddedness is
intended as a strong type of **social situatedness**. It is defined as the extent to which modelling the
behaviour of an agent requires the inclusion of other agents as individuals rather than as an
undifferentiated whole. Possible consequences of the presence of social embedding and ways to check
for it are discussed. A model of co-developing agents is exhibited which demonstrates the possibility of
social embedding. This is an extension of Brian Arthur’s ‘El Farol Bar’ model, with added learning and
communication. Some indicators of social embedding are analysed and some possible causes of social
embedding are discussed. It is suggested that social embeddedness may be an explanation of the causal
link between the social situatedness of the agent and it employing a constructivist strategy in its
modelling.

\\