3,999 research outputs found
Implementing imperfect information in fuzzy databases
Information in real-world applications is often
vague, imprecise and uncertain. Ignoring the inherent imperfect
nature of real-world will undoubtedly introduce some deformation of human perception of real-world and may eliminate several
substantial information, which may be very useful in several
data-intensive applications. In database context, several fuzzy
database models have been proposed. In these works, fuzziness
is introduced at different levels. Common to all these proposals is
the support of fuzziness at the attribute level. This paper proposes
first a rich set of data types devoted to model the different kinds
of imperfect information. The paper then proposes a formal
approach to implement these data types. The proposed approach
was implemented within a relational object database model but it
is generic enough to be incorporated into other database models.ou
Can Quantum Lattice Fluctuations Destroy the Peierls Broken Symmetry Ground State?
The study of bond alternation in one-dimensional electronic systems has had a
long history. Theoretical work in the 1930s predicted the absence of bond
alternation in the limit of infinitely long conjugated polymers; a result later
contradicted by experimental investigations. When this issue was re-examined in
the 1950s it was shown in the adiabatic limit that bond alternation occurs for
any value of electron-phonon coupling. The question of whether this conclusion
remains valid for quantized nuclear degrees of freedom was first addressed in
the 1980s. Since then a series of numerical calculations on models with gapped,
dispersionless phonons have suggested that bond alternation is destroyed by
quantum fluctuations below a critical value of electron-phonon coupling. In
this work we study a more realistic model with gapless, dispersive phonons. By
solving this model with the DMRG method we show that bond alternation remains
robust for any value of electron-phonon coupling
Air Corporate Governance and Suspicion of Corruption in Supply Chain Management: The Case of Tunis Air Airlines
The corporate governance of airlines companies is not a well studied area. As corruption is a criminal act, the issue is sensitive, and the doors are not opened for researchers. This article aims to contribute to the scarce literature surrounding this topic in order to overcome the lack of research. By staying studying this topic at a general lever and analyzing most of the supply chain activities of real airline companies, we can detect which activities within the supply chain present the most potential where corruption could take place. Propositions will be developed about the characteristics that need to be built into the value chain activities to be robust against corruption. These analyses and propositions are grounded in a case study of the Tunisian airline, Tunis Air. Although this company is not among the biggest airlines in the world, it’s governance could be a structural example in this area of study
Vibration Control in MEMS Resonator Using Positive Position Feedback (PPF) Controller
In this paper, the vibration of a micro-electromechanical resonator with positive position feedback controller is studied. The analytical results are obtained to the first order approximation by using the multiple scale perturbation technique. The stability of the steady-state solution is presented and studied applying frequency response equations near the simultaneous primary and internal resonance cases. The effects of the controller and some system parameters on the vibrating system are studied numerically. The main result of this paper indicates that it is possible to reduce the vibration for the resonator system
Organized Current Patterns in Disordered Conductors
We present a general theory of current deviations in straight current
carrying wires with random imperfections, which quantitatively explains the
recent observations of organized patterns of magnetic field corrugations above
micron-scale evaporated wires. These patterns originate from the most efficient
electron scattering by Fourier components of the wire imperfections with
wavefronts along the direction. We show that long range
effects of surface or bulk corrugations are suppressed for narrow wires or
wires having an electrically anisotropic resistivity
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