SEMI2

Seminal Seminars

Wide-audience Scientific Seminars of IST-Tagus



Abstracts

  • 9th of July

    Sensors: If a few can do so much for so many, imagine what a network can do!    <slides>
    by Rui Rocha

    Perhaps the first and most thorough concretization of Mark Weiser's vision of Ambient Intelligence is the Wireless Sensor Network concept. Indeed, such approach is based on the idea that computing is pervasively integrated in the environment, becoming indistinguishable from it. Moreover, underlying this concept is the assumption that sensing a range of physical phenomena, rather than just data input, becomes a key aspect of small, embedded  computers that communicate with each other to organize and coordinate their actions.

    This talk will address the major challenges and opportunities concerning Sensor Networks, presenting and discussing the key issues that characterize this type of networks and what new networking paradigms are involved in its design, deployment and operation. 


    References

    [ECPS] Deborah Estrin, David Culler, Kris Pister and Gaurav Sukhatme; Connecting the Physical World with Pervasive Networks; IEEE Pervasive Computing, Vol. 1, No. 1, pp. 59-69.



  • 25th of June

    Quantum bits and their applications
    by Yasser Omar

    Quantum Information Theory is a new area of Physics and Information Science that explores the strange properties of Quantum Mechanics to encode, transmit, store and process information [D,BB]. Over the last decade, we understood how to take advantage of these properties for revolutionary applications, such as teleportation of quantum states, communications protected against eavesdropping in a completely secure way or computers astonishingly faster than the current ones (but for the time being limited to a small number of quantum bits!). This rapid progress in the field happened both at the theoretical and at the experimental level and contributed to improve our understanding of Quantum Mechanics. In this talk I will try to present the essential ideas behind these applications, as well as the challenges for this new area of Science.


    References

    [D] D. Deutsch, Quantum theory, the Church-Turing principle and the universal quantum computer, in Proc. R. Soc. A 400, 97 (1985).
    [BB] C. H. Bennett and G. Brassard, Quantum cryptography: Public key distribution and coin tossing, in Proc. IEEE International Conference on Computers, Systems, and Signal Processing, IEEE, New York, 175 (1984).


  • 11th of June

    What is so special in the Tomasulo Hardware Algorithm?     <slides>
    por Leonel Sousa

    This "Seminário Seminal" revisits the original Tomasulo's paper about his hardware algorithm [T]. Although it was proposed forty years ago to exploit the existence of multiple execution units in old computers, it is still a quite an important algorithm in nowadays powerful general purpose processors. This algorithm associates simple common data busing with a register tagging scheme to allow simultaneous execution of independent instructions, while preserving the essential precedences inherent in programs. It has played a central role to take advantage of the exponential growing number of transistors available in a chip (Moore law). The seminar is also a single tribute to the memory of Dr. Tomasulo, recently deceased.


    References

    [T] R. M. Tomasulo, An Efficient Algorithm for Exploiting Multiple Arithmetic Units, IBM Journal, 25-33 (1967).


  • 28th of May

    When probabilities take the leading role in finances
    by Cláudia Philippart

    In 1997 Robert Merton and Myron Scholes won the Nobel Prize in Economic Sciences, with their work on valuation of stock options, in collaboration with Fischer Black, who died in 1995.
    The famous Black-Scholes model is very interesting and rich, also in math terms, as it in a certain way combines stochastic differential equations and parabolic differential equations.
    In this seminar we talk about this model, in the context of option pricing.  We will see why in this strange world we have strange things, like Wiener processes, martingale measures, Itô integrals, ...; all freak structures!
    After an excursion in this lunatic world, we will give two particular examples of applications, different from option pricing.  Namely we will present, very briefly, the problem of relocation of large companies and the investment in high speed rate services (like the polemic investment in the TGV, in Portugal) using this kind of approach.
    At the end, the audience will have a clue of how brokers and big investment companies price their services and assets!


    References

    [BS]  F. Black, M. Scholes, The Pricing of Options and Corporate Liabilities, Journal of Political Economy, 81 (3): 637-654 (1973).
    [M] R. Merton, Theory of Rational Option Pricing, Bell Journal of Economics and Management Science, Vol. 4: 141-183 (1973).



  • 14th of May

    Nanophysics and Nanotechnology of Thin Magnetic Films        <resumo>
    por Mircea Rogalski

    The development of artificial magnetic structures at the nanometric scale, and in particular of thin films and multilayered systems, is related to the new phenomena that were discovered in the last years, such as giant magnetoresistence [*], interlayer magnetic coupling, magnetic tunnel effect or spin dependent transport.  The characterization of structural, magnetic and transport properties by a set of techniques of physics and material engineering has had a relevant role in the research for new systems and phenomena and for their technological application.

    This talk will present both the standard principles and the current practice in the deposition of various magnetic nanostructures and its spectroscopic characterization by nuclear resonance methods, and will highlight the state of the art, the difficulties, and the current and potential applications.

    References

    [*]  M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, G. Creuzet, A. Friederich and J. Chazelas, Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices, Physical Review Letters, vol. 6, num. 21 (1988).

    [*] G. Binasch, P. Grünberg, F. Saurenbach and W. Zinn, Enhanced magnetoresistence in layered magnetic structures with antiferromagnetic interlayer exchange, Physical Review Letters, vol. 39, num. 7 (1989).


  • 30th of April

    Abstract Interpretation: The Genie inside Compiler Data Flow Analysis
    por Pedro Diniz

    Abstract interpretation is the basic technique at the core of all static data-flow analyses used in advanced compilers today.  It allows compiler to reason at compile time about values computed at run-time. Despite its inherent limitations, the results of these analyses enable compilers to perform sophisticated transformations that lead to increased program performance metrics while guaranteing the fundamental cornerstone of any compiler transformation: correctness.

    In this talk we will show through a simple example the use of abstract interpretation and motivate its generalized use in the definitions of data-flow analysis frameworks.


    References

    [CC] P. Cousot and R. Cousot, Abstract interpretation: a unified lattice model for static analysis of programs by construction or approximation of fixpoints, In Conference Record of the Sixth Annual ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, (1977), 238--252.



  • 16th of April

    Silicon Based Servers, Carbon Based Servers and Organizational Self-Awareness
    por José Tribolet

    Individual Self-awareness is a pre-requisite for effective action, decision-making and learning processes. Self-aware beings know who they are, how they do things and what they (and others) are doing at any particular moment. Whereas innate in individual human beings, self-awareness in organizations must be built and maintained by continuous interactions among their members. Although currently supported by a variety of IS/IT tools, organizational self-awareness is typically fragmented, frequently inconsistent and most of all, outdated. The use of organizational models seems a promising means in achieving this end. However, this is a challenging task requiring the integration of several approaches and the definition and implementation of model acquisition mechanisms.

    From our point of view, enterprise models are an essential communication tool in supporting and enhancing organization’s self-awareness. Organizational modeling has a long tradition in organizational and management sciences. In these fields, the main goal is to provide ways of thinking about the organization and to produce management principles and theories based on these ways of thinking. These models, described in natural language and with a high level of abstraction, are limited to human use and lead to different interpretations.

    Computer Science and Engineering have also addressed organizational modeling activities. These models are commonly referred as Enterprise Architectures or Enterprise Ontologies and aim at facilitating the design and implementation of Information Systems and Technologies (IS/IT) aligned with organizations. IS/IT models are mainly used as communication tool. Consequently, they are described using more formal syntax and semantics, enabling its processing by automated agents and reducing inconsistent interpretations. However, current enterprise representations are presently restricted to concerns relevant for participants and stakeholders of IS/IT development, acquisition or implementation projects. Moreover, these representations assume a rather static, mechanistic and deterministic view of the organization.

    Modeling the organization for its self-awareness is a much more challenging task. It requires integrating approaches coming from organizational and IS fields, to capture: (1) structural and dynamic aspects, (2) formal (hard) and informal (soft) sides and (3) different viewpoints and levels of details of organizations. Moreover, it entails capturing organization’s evolution.

    A first step in achieving this end is the definition of a conceptual framework to enable the construction of several types of models capable of representing organizational routines, as well as deliberation and change processes. This conceptual framework must also allow the mapping between the different models.

    The new field of Organizational Engineering attemtps to provide solid scientific basis for such an holistic, integrated and dynamic conceptual frework, capable of supporting the emerging bionic properties of the Self-Aware Organizations of the XXI Century, which are truly semantic webs of carbon-based (i.e. Humans) and silicon-based servers (i.e. Computers), dinamically orchestrationg through their transactions the enactment of the organizational processes.




  • 2nd of April

    The Library of Babel -- Information and Entropy
    by Andreas Wichert
The books of the library of Babel [B] contain every possible ordering of just a few basic characters (letters, spaces and punctuation marks). Though the majority of the books in this universe are pure gibberish, the library also must contain, somewhere, every coherent book ever written, or that might ever be written, and every possible permutation or slightly erroneous version of every one of those books.

However not all characters appear with the same probability, the probability is defined by the corresponding language in which we write or read the book. The corresponding probability can be represented by the information, known as information entropy, which is usually expressed by the average number of bits needed for storage. Bit, introduced 1944 is the smallest information unit corresponding as quantity of yes-or-no answers. We can represent each character by some bits. Each bit must be stored in a state of some physical system.

The real physical world gives us the ability to represent superposition of bits, the so called qubits. It means a one and a zero exist at the same time and can be manifested in two different (physical) worlds. Qubits give us a way to represent the library of Babel in form of a book. The book represents the superposition of all possible books. We can increase our chance of accessing a more meaningful book in our own world with the aid of Unitary operators which manipulate the probabilities.


References

[B] J. L. Borges, La biblioteca de Babel, in Ficciones (1944).



  • 12th of March -- Opening

    Symplectic Mathematics: Geometry and Topology
    by Miguel Abreu
The last 25 years have seen plenty of mathematical developments where the word "symplectic" shows up, i.e. where a "skew-symmetric non-degenerate bilinear form" determines the questions under study.  Some of these developments are said to be part of Symplectic Geometry, while others are said to be part of Symplectic Topology.

For example, questions related with the "moment map" and the "Atiyah-Guillemin-Sternberg convexity theorem" (cf. [A] and [GS]) are usually considered as part of Symplectic Geometry, while questions related to "holomorphic curves" and "Gromov's compactness theorem" (cf. [G]) are usually considered as part of Symplectic Topology.

The first part of this seminar will be an introduction to symplectic mathematics. In the second part the Geometry/Topology dichotomy will be illustrated through the discussion of the following two problems:
  • Geometry: study of "symplectic toric manifolds";
  • Topology: study of the "symplectomorphism group" of a "symplectic manifold".

The meaning of all the expressions under quotes in this abstract will be explained during the seminar.


References

[A] M. F. Atiyah, Convexity and commuting Hamiltonians, Bull. London Math. Soc. 14 (1982), 1-15.
[GS] V. Guillemin and S. Sternberg, Convexity properties of the moment mapping, Invent. Math. 67 (1982), 491-513.
[G] M. Gromov, Pseudo holomorphic curves in symplectic manifolds, Invent. Math. 82 (1985), 307-347.


Contacts

If you would like to contribute with a presentation or sugest a speaker to be invited, contact ana.matos@ist ...