38 research outputs found
Formulation of linguistic regression model based on natural words
When human experts express their ideas and thoughts, human words are basically employed in these expressions. That is, the experts with much professional experiences are capable of making assessment using their intuition and experiences. The measurements and interpretation of characteristics are taken with uncertainty, because most measured characteristics, analytical result, and field data can be interpreted only intuitively by experts. In such cases, judgments may be expressed using linguistic terms by experts. The difficulty in the direct measurement of certain characteristics makes the estimation of these characteristics imprecise. Such measurements may be dealt with the use of fuzzy set theory. As Professor L. A. Zadeh has placed the stress on the importance of the computation with words, fuzzy sets can take a central role in handling words [12, 13]. In this perspective fuzzy logic approach is offten thought as the main and only useful tool to deal with human words. In this paper we intend to present another approach to handle human words instead of fuzzy reasoning. That is, fuzzy regression analysis enables us treat the computation with words. In order to process linguistic variables, we define the vocabulary translation and vocabulary matching which convert linguistic expressions into membership functions on the interval [0–1] on the basis of a linguistic dictionary, and vice versa. We employ fuzzy regression analysis in order to deal with the assessment process of experts from linguistic variables of features and characteristics of an objective into the linguistic expression of the total assessment. The presented process consists of four portions: (1) vocabulary translation, (2) estimation, (3) vocabulary matching and (4) dictionary. We employed fuzzy quantification theory type 2 for estimating the total assessment in terms of linguistic structural attributes which are obtained from an expert
Ab initio simulations of the kinetic properties of the hydrogen monomer on graphene
The understanding of the kinetic properties of hydrogen (isotopes) adatoms on
graphene is important in many fields. The kinetic properties of
hydrogen-isotope (H, D and T) monomers were simulated using a composite method
consisting of density functional theory, density functional perturbation theory
and harmonic transition state theory. The kinetic changes of the magnetic
property and the aromatic bond of the hydrogenated graphene during the
desorption and diffusion of the hydrogen monomer was discussed. The vibrational
zero-point energy corrections in the activation energies were found to be
significant, ranging from 0.072 to 0.205 eV. The results obtained from
quantum-mechanically modified harmonic transition state theory were compared
with the ones obtained from classical-limit harmonic transition state theory
over a wide temperature range. The phonon spectra of hydrogenated graphene were
used to closely explain the (reversed) isotope effects in the prefactor,
activation energy and jump frequency of the hydrogen monomer. The kinetic
properties of the hydrogen-isotope monomers were simulated under conditions of
annealing for 10 minutes and of heating at a constant rate (1.0 K/s). The
isotope effect was observed; that is, a hydrogen monomer of lower mass is
desorbed and diffuses more easily (with lower activation energies). The results
presented herein are very similar to other reported experimental observations.
This study of the kinetic properties of the hydrogen monomer and many other
involved implicit mechanisms provides a better understanding of the interaction
between hydrogen and graphene.Comment: Accepted by J. Phys. Chem.