See all upcoming seminars in LäsIT and seminar web pages at the homepage for the PhD studentseminars, TDB, Vi2, Theory and Applications Seminars (TAS) @ UpMARC., Department of Mathematics and The Stockholm Logic Seminar.

Half-time seminar
Tomorrow (25 Apr)
Gustav Björdal: Declarative Local-Search Methods
Location: ITC 2446, Time: 13:30

Discrete optimisation problems are very important to solve for society, and include problems such as routing, scheduling, planning, and packing. These problems are NP-hard or worse in general, but can usually be solved using dedicated software, called solvers. Solvers are either specialised for a problem class (say routing) or general-purpose. General-purpose solvers require a declarative mathematical formulation of the problem, called a model, as part of their input, and are continuing to become more and more powerful and usable with advancements being made to both the underlying algorithms and the languages in which models are formulated. More recently, dedicated modelling languages that are solver-independent have emerged. One such language (and open-source framework), called MiniZinc, tries to unify different types of solvers under a shared language.

My research revolves around making solvers based on an optimisation method known as local search available via MiniZinc. To do so, I have developed the first interface between a local-search solver and MiniZinc. I am continuing to identify and address local-search specific challenges that arise from such an interface. Furthermore, I have made extensions to the MiniZinc language that allow the efficient use of local-search solvers in a more declarative manner than previously.

In this half-time presentation I will explain what all of these words mean and give a high-level overview of my research so far, while hinting at what is to come. The targeted audience for this presentation will be anyone with a computer science background.

Disputation | Dissertation
8 May
Kalyan Ram Ayyalasomayajula: Learning based segmentation and generation methods for handwritten document images
Location: TLS, Carolina Rediviva Library, Time: 9:00

Kalyan Ram Ayyalasomayajula will present and defend his PhD thesis Learning based segmentation and generation methods for handwritten document images.
Opponent: Professor Nicholas Howe, Department of Computer Science, Smith College.
Supervisors: Anders Brun and Philip Malmberg.

DiVA includes an abstract and the full text of the thesis.

Licentiatseminarium | Licentia
13 May
Viktor Bro: Volterra Modeling of the Human Smooth Pursuit System in Health and Disease
Location: ITC 1111, Time: 13:15

Abstract: This thesis treats the identification of Volterra models of the human smooth pursuit system from eye-tracking data. Smooth pursuit movements are gaze movements used in tracking of moving targets and controlled by a complex biological network involving the eyes and brain. Because of the neural control of smooth pursuit, these movements are affected by a number of neurological and mental conditions, such as Parkinson's disease. Therefore, by constructing mathematical models of the smooth pursuit system from eye-tracking data of the patient, it may be possible to identify symptoms of the disease and quantify them. While the smooth pursuit dynamics are typically linear in healthy subjects, this is not necessarily true in disease or under influence of drugs. The Volterra model is a classical black-box model for dynamical systems with smooth nonlinearities that does not require much a priori information about the plant and thus suitable for modeling the smooth pursuit system.

The contribution of this thesis is mainly covered by the four appended papers. Papers~I-III treat the problem of reducing the number of parameters in Volterra models with the kernels parametrized in Laguerre functional basis (Volterra-Laguerre models), when utilizing them to capture the signal form of smooth pursuit movements. Specifically, a Volterra-Laguerre model is obtained by means of sparse estimation and principal component analysis in Paper~I, and a Wiener model approach is used in Paper~II. In Paper~III, the same model as in Paper~I is considered to examine the feasibility of smooth pursuit eye tracking for biometric purposes. Paper~IV is concerned with a Volterra-Laguerre model that includes an explicit time delay. An approach to the joint estimation of the time delay and the finite-dimensional part of the Volterra model is proposed and applied to time-delay compensation in eye-tracking data.

21 May
Serkan Saritas: Signaling Games in Networked Systems
Location: Room: 72121, House 7, Floor 2, Ångström, Time: 13:15

Abstract: We investigate decentralized quadratic cheap talk and signaling game problems when the decision makers (an encoder and a decoder) have misaligned objective functions. We first extend the classical results of Crawford and Sobel on cheap talk to multi-dimensional sources and noisy channel setups, as well as dynamic (multi-stage) settings. Under each setup, we investigate both Nash (simultaneous) and Stackelberg (leader-follower) equilibria. We show that for scalar cheap talk, the quantized nature of Nash equilibrium policies holds for arbitrary sources; whereas Nash equilibria may be of non-quantized nature, and even linear for multi-dimensional setups. All Stackelberg equilibria policies are fully informative, unlike the Nash setup. For noisy signaling game, a Gauss-Markov source is to be transmitted over a memoryless additive Gaussian channel. Here, conditions for the existence of affine equilibria, as well as informative equilibria are presented and a dynamic programming formulation is obtained for linear equilibria. For all setups, conditions under which equilibria are non-informative are derived through information theoretic bounds. We then provide a different construction for signaling games in view of the attacker-defender game setting under the Stackelberg equilibrium. That is, the defender (control center), as a receiver, is the leader, and the attacker (adversarial sensor), as a transmitter, is the follower. The equilibrium strategies and the associated costs are characterized for uniformly distributed variables and quadratic objective functions, and an analysis on the uniqueness of the equilibrium is provided. Our findings reveal drastic differences in signaling behavior under team and game setups, which have consequences in networked control applications. Furthermore, we provide conditions on when affine policies may be optimal in decentralized multi-criteria control problems and for the presence of active information transmission even in strategic environments. Bio: Serkan Sar?ta? is a Postdoctoral Researcher at the Division of Decision and Control Systems, KTH Royal Institute of Technology since September 2018. He received his B.Sc. degree in Electrical and Electronics Engineering, M.S. degree in Computer Engineering and Ph.D. degree in Electrical and Electronics Engineering from Bilkent University, Turkey, in 2010, 2013, and 2018, respectively. He has been a visiting research student at the Department of Mathematics and Statistics at Queen’s University in Kingston, Canada for five months in 2015. His main research interests include security of cyber-physical systems, networked control systems, game theory, communication systems, and information theory.

See also the list of all upcoming seminars.

Internal seminars. Lecturers may be either internal or external.