12 research outputs found
Evidential Communities for Complex Networks
Community detection is of great importance for understand-ing graph structure
in social networks. The communities in real-world networks are often
overlapped, i.e. some nodes may be a member of multiple clusters. How to
uncover the overlapping communities/clusters in a complex network is a general
problem in data mining of network data sets. In this paper, a novel algorithm
to identify overlapping communi-ties in complex networks by a combination of an
evidential modularity function, a spectral mapping method and evidential
c-means clustering is devised. Experimental results indicate that this
detection approach can take advantage of the theory of belief functions, and
preforms good both at detecting community structure and determining the
appropri-ate number of clusters. Moreover, the credal partition obtained by the
proposed method could give us a deeper insight into the graph structure
Asymmetry through time dependency
Given a single network of interactions, asymmetry arises when the links are
directed. For example, if protein A upregulates protein B and protein B
upregulates protein C, then (in the absence of any further relationships between them) A
may affect C but not vice versa. This type of imbalance is reflected in the associated
adjacency matrix, which will lack symmetry. A different type of imbalance can arise when
interactions appear and disappear over time. If A meets B today and B meets C tomorrow,
then (in the absence of any further relationships between them) A may pass a message or
disease to C, but not vice versa. Hence, even when each interaction is a two-way exchange,
the effect of time ordering can introduce asymmetry. This observation is very closely
related to the fact that matrix multiplication is not commutative. In this work, we
describe a method that has been designed to reveal asymmetry in static networks and show
how it may be combined with a measure that summarizes the potential information flow
between nodes in the temporal case. This results in a new method that quantifies the
asymmetry arising through time ordering. We show by example that the new tool can be used
to visualize and quantify the amount of asymmetry caused by the arrow of time
Predicting Missing Links via Local Information
Missing link prediction of networks is of both theoretical interest and
practical significance in modern science. In this paper, we empirically
investigate a simple framework of link prediction on the basis of node
similarity. We compare nine well-known local similarity measures on six real
networks. The results indicate that the simplest measure, namely common
neighbors, has the best overall performance, and the Adamic-Adar index performs
the second best. A new similarity measure, motivated by the resource allocation
process taking place on networks, is proposed and shown to have higher
prediction accuracy than common neighbors. It is found that many links are
assigned same scores if only the information of the nearest neighbors is used.
We therefore design another new measure exploited information of the next
nearest neighbors, which can remarkably enhance the prediction accuracy.Comment: For International Workshop: "The Physics Approach To Risk:
Agent-Based Models and Networks", http://intern.sg.ethz.ch/cost-p10
costeening
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Crescimento e metabolismo do nitrogênio em juvenis de trachinotus marginatus alimentados com diferentes níveis proteicos
O objetivo deste trabalho foi avaliar o crescimento e alterações no metabolismo do nitrogênio, além da composição do fígado e do músculo de juvenis de pampo Trachinotus marginatus alimentados com 43, 54 ou 64% de proteína bruta (PB43, PB54 e PB64, respectivamente). Grupos de 10 juvenis (1,47±0,14g) foram estocados em nove tanques de 50L, em sistema de recirculação de água marinha, durante 55 dias, alimentados quatro vezes ao dia com as rações pré-definidas. O ganho em peso, a taxa de crescimento específico e a conversão alimentar não apresentaram diferença significativa (P>0,05). Contudo, o acréscimo de proteína consumida aumentou o índice hepatossomático e a taxa de excreção de amônia pós-prandial, bem como diminuiu a retenção proteica. Os peixes alimentados com a dieta PB43 apresentaram menor concentração da transaminase glutâmico oxalacética hepática, além de menor concentração de triglicerídeos no músculo e fígado (P0,05), excetuando o maior teor de lipídios da carcaça no tratamento PB43. Concluímos que a melhor utilização da proteína por juvenis de pampo é observada quando eles são alimentados com uma dieta contendo 43% de proteína.The experiment aimed to evaluate the growth, the nitrogen metabolism and liver and muscle composition of juvenile pompano Trachinotus marginatus fed with different protein levels (PB43, PB54, PB64). Groups of 10 juveniles (1.47±0.14g) were stocked in nine tanks with 50L in a marine recirculating aquaculture system during 55 days. Fish were fed four times a day. The weight gain, specific growth rate and feed conversion rate did not present significant differences (P>0.05). However, the increase in protein consumption augmented the hepatosomatic index, the pos prandial ammonia excretion rate and reduced the protein efficiency rate. Fish fed with PB43 presented lower hepatic glutamic oxaloacetic transaminase and lower concentration of triglycerides in muscle and liver (P0.05), with the exception of the lipid content in fish carcass fed with PB43. It is concluded that the better protein utilization in juvenile pompano is observed when they are fed with 43% protein