Publications de Ali Ajdari Rad

Topological Measure Locating the Effective Crossover between Segregation and Integration in a Modular Network

We introduce an easily computable topological measure which locates the effective crossover between segregation and integration in a modular network. Segregation corresponds to the degree of network modularity, while integration is expressed in terms of th ...

American Physical Society2012

Information Processing and Structure of Dynamical Networks

Ali Ajdari Rad

Networks are everywhere and we are confronted with many networks in our daily life. Networks such as Internet, World Wide Web, social, biological and economical networks have been subject to extensive studies in the last decade. The volume of publications ...

EPFL2011

Network community-detection enhancement by proper weighting

Martin Hasler, Ali Ajdari Rad, Alireza Khadivi

In this article, we show how proper assignment of weights to the edges of a complex network can enhance the detection of communities and how it can circumvent the resolution limit and the extreme degeneracy problems associated with modularity. Our general ...

American Physical Society2011

A lower bound for algebraic connectivity based on the connection-graph-stability method

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

This paper introduces the connection-graph-stability method and uses it to establish a new lower bound on the algebraic connectivity of graphs (the second smallest eigenvalue of the Laplacian matrix of the graph) that is sharper than the previously publish ...

Elsevier2011

Information Processing in Complex Networks

Martin Hasler, Ali Ajdari Rad, Alireza Khadivi

2010

Automatic skill acquisition in Reinforcement Learning using connection graph stability centrality

Martin Hasler, Ali Ajdari Rad

Reinforcement Learning (RL) is an approach for training agent's behavior through trial-and-error interactions with a dynamic environment. An important problem of RL is that in large domains an enormous number of decisions are to be made. Hence, instead of ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2010

Community detection enhancement in networks using proper weighting and partial synchronization

Martin Hasler, Ali Ajdari Rad, Alireza Khadivi

A community in a network is a subset of vertices densely connected to each other, but less connected to the vertices outside. Many different approaches have been developed to find such structures in a given network, but the main drawback of most of the ava ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2010

Reservoir optimization in recurrent neural networks using properties of Kronecker product

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

Recurrent neural networks based on reservoir computing are increasingly being used in many applications. Optimization of the topological structure of the reservoir and the internal connection weights for a given task is one of the most important problems i ...

2010

Multiple task learning in recurrent neural networks using layered reservoirs

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

In this paper, to learn multiple tasks sharing same inputs, a two-layer architecture for a reservoir based recurrent neural network is proposed. The inputs are fed into the general workspace layer where the weights are adapted to provide maximum informatio ...

2009

Synchronizability of dynamical networks: different measures and coincidence

Mahdi Jalili, Ali Ajdari Rad

In this paper, we list four different interpretations of synchronizability, study their profile in different network structures and give evidence that they do not coincide, in general. By changing the network topological properties, their behavior is track ...

2009

Comment on Rewiring networks for synchronization

Mahdi Jalili, Ali Ajdari Rad

This is a comment on a recent paper by A. Hagberg and D. A. Schult [Chaos 18, 037105 (2008)]. By taking the eigenratio of the Laplacian of an undirected and unweighted network as its synchronizability measure, they proposed a greedy rewiring algorithm for ...

2009

Reservoir Optimization in Recurrent Neural Networks using Kronecker Kernels

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

In this paper, using the mathematical properties of self-kronecker-production of small size random matrices, a simple but effective method is presented to optimize the reservoir of an echo state network given a certain task. The experimental results invest ...

IEEE2008

Efficient rewirings for enhancing synchronizability of dynamical networks

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

American Institute of Physics2008

Reducing Synchronization Cost in Weighted Dynamical Networks Using Betweenness Centrality Measures

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

In this paper we investigate optimization of synchronization cost in undirected dynamical networks. To do so, proper weights are assigned to the networks’ edges considering node and edge betweenness centrality measures. The proposed method gives near-optim ...

IEEE2008

Enhancing synchronizability of weighted dynamical networks using betweenness centrality

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

By considering the eigenratio of the Laplacian of the connection graph as a synchronizability measure, we propose a procedure for weighting dynamical networks to enhance their synchronizability. The method is based on node and edge betweenness centrality m ...

2008

Multidimensional image enhancement from a set of unregistered differently exposed images

Laurence Meylan, Sabine Süsstrunk, Patrick Vandewalle, Ali Ajdari Rad

If multiple images of a scene are available instead of a single image, we can use the additional information conveyed by the set of images to generate a higher quality image. This can be done along multiple dimensions. Super-resolution algorithms use a set ...

2007

Enhancing synchronizability of dynamical networks using the connection graph stability method

Martin Hasler, Mahdi Jalili, Ali Ajdari Rad

Dynamical networks with diffusive couplings are investigated from the point of view of synchronizability. Arbitrary connection graphs are admitted but the coupling is symmetric. Networks with equal interaction coefficients for all edges of the interaction ...

2007