Browsing by Subject "Special class"

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    FPTAS for half-products minimization with scheduling applications
    (Elsevier, 2008) Erel, E.; Ghosh, J. B.
    A special class of quadratic pseudo-boolean functions called "half-products" (HP) has recently been introduced. It has been shown that HP minimization, while NP-hard, admits a fully polynomial time approximation scheme (FPTAS). In this note, we provide a more efficient FPTAS. We further show how an FPTAS can also be derived for the general case where the HP function is augmented by a problem-dependent constant and can justifiably be assumed to be nonnegative. This leads to an FPTAS for certain partitioning type problems, including many from the field of scheduling.
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    On the boundary control of Kirchhoff's nonlinear string
    (IFAC, 2007) Morgül, Ömer; Shahruz, S. M.
    In this paper we propose two new classes of controllers which stabilize Kirchhoff's nonlinear string by using boundary control techniques. We assume that the boundary displacement is the only available measurement. The classes of controllers proposed in this paper are related to the positive real controllers. One of the classes generalizes a special class of such stabilizing controllers which is already proposed in the literature and the other one is new.
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    Uncertainty and dissipation
    (Katholieke Universiteit Leuven, 2012-09) Carcaterra, A.; Akay, Adnan
    This paper discusses the question of the energy confinement in mechanical structures in the light of the uncertainties affecting the natural frequencies of the system. More precisely, recent studies have shown that energy can be introduced to a linear system with near irreversibility, or energy within a system can migrate to a subsystem nearly irreversibly, even in the absence of dissipation, provided that the system has a particular natural frequency distribution. In this paper, the case of uncertainties in the system's natural frequencies is discussed and a remarkable statistical property of the natural frequency is derived for permanent energy confinement within a part of the system. The results demonstrate the existence of a special class of linear non-dissipative dynamic systems that exhibit nearly-irreversible energy confinement (IEC) if they satisfy a minimum-variance-response (MIVAR) property. In this case, if the probability density function of the natural frequencies has a special distribution, the conservative system shows an unexpected decaying impulse response. © (2012) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved.