Speaker: Prof. T. Laffey Abstract: Let σ = (λ_1,...,λ_n) be a list of complex numbers which we aim to realize constructively as the spectrum of a nonnegative matrix. Most constructions available in the literature rely on building matrices related to companion matrices from the polynomial f(x) = (x-λ_1)...(x-λ_n). Kim, Ormes and Roush (JAMS 2000) showed how certain formal power series related to f(x), which have all coefficients, other than the leading one, negative, can be used in finding constr...
Oct 16, 2011•44 min
Speaker: Prof. R. Loewy Abstract: Let K be a proper (i.e., closed, pointed, full and convex) cone in R^n. We consider A∈R^(n×n) which is K-primitive, that is, there exists a positive integer l such that A^l.x ∈ int K for every 0≠x∈K. The smallest such l is called the exponent of A, denoted by γ(A). For a polyhedral cone K, the maximum value of γ(A), taken over all K-primitive matrices A, is denoted by γ(K). Our main result is that for any positive integers m,n, 3 ≤ n ≤ m, the maximum value of γ(...
Oct 16, 2011•49 min
Speaker: Prof. S. Friedland Abstract: In this talk we will discuss a number of generalizations of results on nonnegative matrices to nonnegative tensors as: irreducibility and weak irreducibility, Perron-Frobenius theorem, Collatz-Wielandt characterization, Kingman's inequality, Karlin-Ost and Friedland theorems, tropical spectral radius, diagonal scaling, Friedland-Karlin inequality, nonnegative multilinear forms.
Oct 16, 2011•44 min
Speaker: Prof. G. Bianchi Abstract: In this talk we address the following question: What is the minimum theoretical delay performance achievable by an overlay peer-to-peer streaming system where the streamed content is subdivided into chunks? We first start to show that, when posed for chunk-based systems, and as a consequence of the store-and-forward way in which chunks are delivered across the network, this question has a fundamentally different answer with respect to the case of systems where...
Aug 10, 2011•1 hr 16 min
Speaker: Prof. J. Leonard Abstract: This talk will have two parts. In part one, we will review recent progress in mobile robotics, focusing on the problems of simultaneous mapping and localization (SLAM) and cooperative navigation of mobile sensor networks. The problem of SLAM is stated as follows: starting from an initial position, a mobile robot travels through a sequence of positions and obtains a set of sensor measurements at each position. The goal is for the mobile robot to process the sen...
Aug 08, 2011•1 hr 6 min
Speaker: Dr. T. Röfer Abstract: Building the software for a competitive robot soccer team is a challenging task. The robots have to perceive their environment, estimate where they and the other relevant object are located on the field, decide what to do, and execute those decisions. All this has to happen in real-time, on-board the robots, with limited computing power, and not only for a single robot, but for the whole team. The lecture will give a survey of these tasks, using the methods used b...
Aug 08, 2011•1 hr 18 min
Speaker: C. Walz Abstract: A first introduction to R.
Jun 02, 2011•59 min
Speaker: Dr. V. Lazzarini Abstract: Non-linear distortion methods form a set of elegant and computationally economic methods of synthesis and processing for musical applications. Among these, we find the famous Frequency Modulation synthesis, as developed by Chowning and made popular by Yamaha. In addition, various other techniques, including Discrete Summation Formulae, Waveshaping and Phase distortion, can be cast in the same group (and often be given alternative interpretations) of non-linear...
Mar 23, 2011•1 hr 6 min
Speaker: Dr. J. Petravic Abstract: In HIV dynamics models, it is commonly assumed that HIV-infected cells all have the same viral production and death rates. We explored the dynamics of viral production and death in vitro to determine the validity of this assumption. We infected human cells with HIV-1 constructs that expressed enhanced green fluorescent protein (EGFP) and determined the amount of viral proteins produced by infected cells. Analysis of the flow cytometry data showed that the produ...
Mar 05, 2011•55 min
Speaker: Dr. Y. Setty Abstract: In recent years, we have used software engineering tools to develop reactive models to simulate and analyze the development of organs. The modeled systems embody highly complex and dynamic processes, by which a set of precursor stem cells proliferate, differentiate and move, to form a functioning tissue. Three organs from diverse evolutionary organisms have been thus modeled: the mouse pancreas, the C. elegans gonad, and partial rodent brain development. Analysis ...
Feb 23, 2011•41 min
Speaker: Dr. I. Radusch Abstract: Future drivers and vehicles will benefit from upcoming integrated communication devices three-fold. Communication will increase safety and efficiency in traffic as well as making driving more enjoyable. Upcoming field operational tests will assess if available standards and implementations are ready for wide scale deployment. Additionally, simulation environments such as VSimRTI allow comprehensive pre-validation of novel vehicle functions utilizing vehicle-2-x ...
Feb 18, 2011•1 hr 9 min
Speaker: Dr. J. Wenus Abstract: Microscopy of living cells is heavily employed in biomedicine to understand the mechanisms of disease progression and to develop novel pharmaceuticals. In particular, confocal microscopy which relies on laser-based excitation of fluorescent cellular biomarkers is frequently used for understanding molecular actions of therapeutic drugs to abnormal cells. However, prolonged exposure to highly energetic laser radiation often leads to light induced cell death before a...
Dec 15, 2010•38 min
Speaker: Dr. S. Dey Abstract: In this talk, we consider a wideband spectrum sharing system where a secondary user can share a number of orthogonal frequency bands each licensed to a distinct primary user. We address the problem of optimum secondary transmit power allocation for its ergodic capacity maximization subject to an average sum (across the bands) transmit power constraint and individual average interference constraints on the primary users. The major contribution of our work lies in con...
Jul 14, 2010•59 min
Speaker: Dr. H. Touchette Abstract: The theory of large deviations, initiated by Cramer in the 1930s and later developed by Donsker and Varadhan in the 1970s, is an active field of probability theory that finds applications in many subjects, including statistics, finance, actuarial mathematics, engineering, and physics. Its use in physics dates back to the work of Ruelle, Lanford, and the late John Lewis, among others, who used concepts of large deviations in the 1970s and 1980s to study equilib...
Mar 24, 2010•54 min
Speaker: Dr. C. Bordenave Abstract: Consider N queues with non-homogeneous packet arrivals. The queues share a common communication channel. At the beginning of each timeslot, if queue i has a packet, it attempts to access the channel with probability p_i. This attempt is successful when no other queue attempts to access the channel. For arbitrary N, the stability region of such queuing system is a long standing open problem. However as the number of queues N goes to infinity, it is possible to ...
Mar 03, 2010•56 min
Speaker: Prof. M. E. Valcher Abstract: Abstract: Positive switched systems typically arise to cope with two distinct modeling needs. On the one hand, switching among different models mathematically formalizes the fact that the system laws change under different operating conditions.On the other hand, the variables to be modeled may be quantities that have no meaning unless positive (temperatures, pressures,population levels, ...). In this talk we consider the class of discrete-time positive swit...
Feb 19, 2010•43 min
Speaker: Prof. C. Seoighe Abstract: We describe a phylogenetic model of protein-coding sequence evolution that includes environmental variables. We apply it to a set of viral sequences from individuals with known human leukocyte antigen (HLA) genotype and include parameters to model selective pressures affecting mutations within immunogenic (epitope) regions that facilitate viral evasion of immune responses. We combine this evolutionary model with a hidden Markov model to identify regions of the...
Dec 09, 2009•1 hr 12 min
Speaker: Dr. C. Molina-París Abstract: T cells are specialised white blood cells that protect the body from infection and are also able to kill infected cells. T cells are characterised by the presence of a special receptor on their cell surface called T cell receptor (TCR). The specificity of the T cell, namely which pathogens it can recognise, is determined by the molecular structure of its TCR. T cells can be classified according to their TCRs. All T cells that have identical TCRs are said to...
Nov 18, 2009•54 min
Speaker: Dr. R. Clement Abstract: Neural responses are often generated by the physical movement of an object or a limb. Each such set of responses corresponds a point on a smooth geometrical surface. To be able to manipulate such a representation the brain assigns coordinates to every point on the surface --- a procedure known as embedding. In the first part of this talk the properties of the early visual system are exploited to produce a model of coordinate space based on features such as colou...
Sep 29, 2009•41 min
Speaker: Dr. N. Pettit Abstract: As part of a wider improvement initiative across all parts of our value chain, Danfoss, in 2007, launched an initiative to significantly improve its product development processes. The goal was to make radical improvements on the dimensions of: value to customer, time to profit, unit cost and quality. In order to do this, we looked around to identify industry-wide accepted best practices to build on. When starting a similar program in production 4 years earlier, t...
Sep 16, 2009•1 hr 13 min
Speaker: Dr. M. Flanagan Abstract: Doubly-generalized low-density parity-check (D-GLDPC) codes offer an attractive compromise between algebraic and random code design philosophies. In this talk we introduce the concept of D-GLDPC codes,and then provide a solution for the asymptotic growth rate of the weight distribution of any D-GLDPC ensemble. This tool is then used for detailed analysis of a case study, namely, a rate-1/2 D-GLDPC ensemble where all the check nodes are (7,4) Hamming codes and a...
Aug 25, 2009•53 min
Speaker: Prof. E.C. Velasco Abstract: Volterra integral and difference equations may be used to model the dynamics of physical systems (viscoelasticity, motion of bodies with reference to hereditary) and biological systems (populations dynamics, biomechanics). In this talk we discuss about asymptotic properties of solutions of both, Volterra integral and Volterra difference equations. For the Volterra difference equations, we derive stability conditions based on the direct Lyapunov method and pr...
Aug 16, 2009•54 min
Speaker: Prof. M. Alanyali Abstract: This talk will touch on wireless coexistence issues that arise due to higher spatial density of spectrum usage. We consider a fairness perspective for autonomous scheduling of transmissions by distinct sessions, subject to constraints that are represented by a conflict graph. The emphasis is on randomized backoff-based CSMA algorithms. The resulting transmission dynamics is represented by a Markovian model whose analysis suggests practical challenges in fair ...
Jun 24, 2009•1 hr 7 min
Speaker: Dr. F. Markowetz Abstract: Cellular mechanisms are driven by interactions between proteins, DNA and RNA, working together in cellular pathways. Current knowledge of information flow in the cell is still very incomplete and dissection of cellular pathways is one of the major challenges of systems biology. Computational approaches integrating heterogeneous genomic data sources into one joint model promise a comprehensive view on cellular processes. However, to be successful, computational...
Jun 10, 2009•49 min
Speaker: Dr. Björn Schelter Abstract: Nowadays, data are recorded with increasing spatio as well as temporal resolution. This calls for new methods to analyze these data sets. Caused by the high spatio as well as temporal resolution of the recorded signals, inference of the causal network structure underlying them becomes feasible. In many applications a detailed analysis of these networks allows deeper insights into the normal functioning or malfunctioning of the system. In Neurology this helps...
May 05, 2009•55 min
Speaker: Dr. Rudolf Kulhavý Abstract: There is a common perception in todays business that the world around us becomes less hierarchical and more networked and flat. While the shift towards a networked and decentralised business environment generally creates more freedom to act, it does not increase automatically the chances of success. Understanding the dynamics of networked systems — in particular the interplay between the performance of an individual node and of the entire network, and the im...
Apr 28, 2009•1 hr 4 min
Speaker: Dr. M. Cryan Abstract: Suppose we are given two lists r and c of positive integers, where r=(r[1],...., r[m]) represents a list of prescribed row sums and c=(c[1], ..., c[n]) is a list of prescribed column sums. We require that (r[1] + ... + r[m]) =(c[1] + ... + c[n]). In this setting, we say that a m-by-n matrix X of non-negative integers is a Contingency Table (for these given row/column values) if X simultaneously satisfies all of the given row and column sums. The problem of determi...
Apr 21, 2009•1 hr 1 min
Speaker: Dr. D. Giustiniano Abstract: ADSL is becoming the standard form of residential and small-business broadband access to the Internet due, primarily, to its low deployment cost. These ADSL residential lines are often deployed with Access Points (AP) that provide wireless connectivity. While the ADSL technology has showed evident limits in terms of capacity, the short-range wireless communication can guarantee a similar or higher capacity. Even more important, it is often possible for a res...
Feb 20, 2009•59 min
Speaker: Dr. W. D. Smith Abstract: We describe a new simple but more powerful form of linear cryptanalysis. It appears to break AES (and undoubtedly other cryptosystems too, e.g. SKIPJACK). *But the break is "nonconstructive". *Even if this break is broken (due to the underlying models inadequately approximating the real world) we explain how AES still could contain "trapdoors" which would make cryptanalysis unexpectedly easy for anybody who knew the trapdoor. We then discuss how to use the theo...
Feb 02, 2009•1 hr 5 min
Speaker: Prof. C. Dovrolis Abstract: The issue of router buffer sizing is still open and significant. Previous work either considers open-loop traffic or only analyzes persistent TCP flows. Our work differs in two ways. First, it considers the more realistic case of non-persistent TCP flows with heavy-tailed size distribution. Second, instead of only looking at link metrics, we focus on the impact of buffer sizing on TCP performance. Through a combination of test bed experiments, simulation, and...
Oct 12, 2008•57 min
