2,377 research outputs found
Comparison of specificity and information for fuzzy domains
This paper demonstrates how an integrated theory can be built on the foundation of possibility theory. Information and uncertainty were considered in 'fuzzy' literature since 1982. Our departing point is the model proposed by Klir for the discrete case. It was elaborated axiomatically by Ramer, who also introduced the continuous model. Specificity as a numerical function was considered mostly within Dempster-Shafer evidence theory. An explicity definition was given first by Yager, who has also introduced it in the context of possibility theory. Axiomatic approach and the continuous model have been developed very recently by Ramer and Yager. They also establish a close analytical correspondence between specificity and information. In literature to date, specificity and uncertainty are defined only for the discrete finite domains, with a sole exception. Our presentation removes these limitations. We define specificity measures for arbitrary measurable domains
Towards autonomous fuzzy control
The efficient implementation of on-line adaptation in real time is an important research problem in fuzzy control. The goal is to develop autonomous self-organizing controllers employing system-independent control meta-knowledge which enables them to adjust their control policies depending on the systems they control and the environments in which they operate. An autonomous fuzzy controller would continuously observe system behavior while implementing its control actions and would use the outcomes of these actions to refine its control policy. It could be designed to lie dormant when its control actions give rise to adequate performance characteristics but could rapidly and autonomously initiate real-time adaptation whenever its performance degrades. Such an autonomous fuzzy controller would have immense practical value. It could accommodate individual variations in system characteristics and also compensate for degradations in system characteristics caused by wear and tear. It could also potentially deal with black-box systems and control scenarios. On-going research in autonomous fuzzy control is reported. The ultimate research objective is to develop robust and relatively inexpensive autonomous fuzzy control hardware suitable for use in real time environments
Determination of ferroelectric compositional phase transition using novel virtual crystal approach
We employ a new method for studying compositionally disordered ferroelectric
oxides. This method is based on the virtual crystal approximation (VCA), in
which two or more component potentials are averaged into a composite atomic
potential. In our method, we construct a virtual atom with the correctly
averaged atomic size and atomic eigenvalues. We have used our new method to
study the composition dependent phase transition in Pb(Zr_{1-x}Ti_x)O_3 lying
between x=0.5 and x=0.4. We correctly predict the experimentally determined
phase transition from the tetragonal phase to a low-temperature rhombohedral
phase between these two compositions.Comment: 7 pages, 2 figures, Proceedings for Fundamental Physics of
Ferroelectrics, Aspen, CO February 13-20, 200
Maximum entropy approach to fuzzy control
For the same expert knowledge, if one uses different &- and V-operations in a fuzzy control methodology, one ends up with different control strategies. Each choice of these operations restricts the set of possible control strategies. Since a wrong choice can lead to a low quality control, it is reasonable to try to loose as few possibilities as possible. This idea is formalized and it is shown that it leads to the choice of min(a + b,1) for V and min(a,b) for &. This choice was tried on NASA Shuttle simulator; it leads to a maximally stable control
Accurate construction of transition metal pseudopotentials
We generate a series of pseudopotentials to examine the relationship between
pseudoatomic properties and solid-state results. We find that lattice constants
and bulk moduli are quite sensitive to eigenvalue, total-energy difference and
tail norm errors, and clear correlations emerge. These trends motivate our
identification of two criteria for accurate transition metal pseudopotentials.
We find that both the preservation of all-electron derivative of tail norm with
respect to occupation and the preservation of all-electron derivative of
eigenvalue with respect to occupation {[Phys. Rev. B {\bf 48}, 5031 (1993)]}
are necessary to give accurate bulk metal lattice constants and bulk moduli. We
also show how the fairly wide range of lattice constant and bulk modulus
results found in the literature can be easily explained by pseudopotential
effects.Comment: submitted to Phys. Rev
Long-Run Effects of Post-Kyoto Policies: Applying a Fully Dynamic CGE model with Heterogeneous Capital
The paper develops a new type of CGE model to predict the effects of carbon policies on consumption, welfare, and sectoral development in the long run. Growth is fully endogenous, based on increasing specialization in capital varieties, and specic in each sector of the economy. The benchmark scenario is calculated based on the endogenous gains from specialization which carry over to policy simulation. Applying the model to the Swiss economy we nd that a carbon policy following the Copenhagen Accord entails a moderate but not negligible welfare loss compared to development without any negative eects of climate change. Energy extensive as well as capital and knowledge intensive sectors prot in the form of increased growth rates.Carbon policy, CGE models, energy and endogenous growth, heterogeneous capital
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