é só apareceres rapaz On Mon, Dec 13, 2010 at 19:10, Paulo Gomes <pauloxgomes@xxxxxxxxx> wrote: > Olá, > sou bolseiro do INESC-ID e gostaria de assistir à apresentação. > Saudações Académicas > Paulo Gomes > > 2010/12/7 Andre Martins <afm+@xxxxxxxxxx <afm%2B@xxxxxxxxxx>> > > TALK ANNOUNCEMENT: >> *********************************************************************** >> >> Priberam Machine Learning Lunch Seminar >> Speaker: Mário Figueiredo (IT) >> Venue: IST Alameda, Sala PA2 (Edifício de Pós-Graduação) >> Date: Tuesday, December 14th, 2010 >> Time: 13:00 >> Lunch will be provided >> >> Title: Network Inference from Co-occurences >> >> Abstract: >> >> Inferring network structures is a central problem arising in numerous >> fields of science and technology, including communication systems, biology, >> sociology, and neuroscience. Unfortunately, it is often difficult, or >> impossible, to obtain data that directly reveal the underlying network >> structure, and so one must infer a network from incomplete data. In this >> talk, we will look at the problem of inferring network structure from >> ``co-occurrence" observations. >> These observations identify which network components (e.g., switches and >> routers, in a communications network, or genes, in a gene regulatory >> network) co-occur in a path, but do not indicate the order in which they >> occur in that path. Without order information, the number of networks that >> are consistent with the data grows exponentially with the size of the >> network (i.e., the number of nodes). Yet, the basic engineering/evolutionary >> principles underlying most >> networks strongly suggest that not all networks consistent with the >> observations are equally likely. In particular, nodes that often co-occur >> are probably closer than nodes that rarely co-occur. This rationale suggests >> modeling co-occurrence observations as independent realizations of a >> Markovian random walk on the network, subjected to a random permutation to >> account for the lack of order information. Treating permutations as missing >> data, allows deriving >> an expectation-–maximization (EM) algorithm for estimating the random walk >> parameters. The model and EM algorithm significantly simplify the problem, >> but the computational complexity of the reconstruction process does grow >> exponentially in the length of each transmission path. For networks with >> long paths, the exact E-step may be computationally intractable. We thus >> propose a polynomial-time Monte Carlo EM algorithm based on importance >> sampling and derive conditions that >> ensure convergence of the algorithm with high probability. Finally, we >> report simulations and experiments with Internet measurements and >> inference of biological networks that demonstrate the promise of this >> approach. >> >> The work reported in this talk was done in collaboration with Prof. >> Michael Rabbat (McGill University, Canada) and Prof. Robert D. Nowak >> (University of Wisconsin, USA). >> >> -- >> >> Bio: Mário A. T. Figueiredo received EE, MSc, PhD, and "Agregado" >> degrees in electrical and computer engineering, all from Instituto >> Superior Técnico (IST), Technical University of Lisbon (TULisbon), Portugal, >> in 1985, 1990, 1994, and 2004, respectively. Since 1994, he has been with >> the faculty of the Department of Electrical and Computer >> Engineering, IST. He is also area and group coordinator at Instituto de >> Telecomunicações, a private not-for-profit research institution. Mário >> Figueiredo spent sabbatical leaves at the Department of Computer Science >> and Engineering, Michigan State University, and the Department >> of Electrical and Computer Engineering, University of Wisconsin-Madison, >> in 1998 and 2005, respectively. He is a Fellow of the IEEE and of the IAPR >> (International Association for Pattern Recognition) and a member of the >> Image, Video, and Multidimensional Signal Processing Technical Committee of >> the IEEE. >> >> Mário Figueiredo's scientific interests include image processing and >> analysis, pattern recognition, statistical learning, and optimization. He >> received the 1995 Portuguese IBM Scientific Prize and the 2008 >> UTL/Santander-Totta Scientific Prize. He is/was associate editor of the >> following journals: IEEE Transactions on Image Processing, IEEE Transactions >> on Pattern Analysis and Machine Intelligence (IEEE-TPAMI), IEEE Transactions >> on Mobile Computing, Pattern Recognition Letters, and Signal Processing. He >> is/was guest co-editor of special issues of the IEEE-TPAMI, the IEEE >> Transactions on Signal Processing, and the IEEE Journal of Selected Topics >> in Signal Processing. Mário Figueiredo was a co-chair of the 2001 and 2003 >> Workshops on Energy Minimization Methods in Computer Vision and Pattern >> Recognition, and has served as a member of >> organizing/program/technical/scientific committees of many >> international conferences, including ICIP, ICASSP, CVPR, ICML, >> ICPR, NIPS, IGARSS, MLSP, IJCNN, and others. >> >> >> >> >> >