Istanbul Technical University

About: Istanbul Technical University is a education organization based out in Istanbul, Turkey. It is known for research contribution in the topics: Fuzzy logic & Large Hadron Collider. The organization has 12889 authors who have published 25081 publications receiving 518242 citations. The organization is also known as: İstanbul Teknik Üniversitesi & Technical University of Istanbul.

Analysis of input-output clustering for determining centers of RBFN

Abstract: The key point in design of radial basis function networks is to specify the number and the locations of the centers. Several heuristic hybrid learning methods, which apply a clustering algorithm for locating the centers and subsequently a linear least-squares method for the linear weights, have been previously suggested. These hybrid methods can be put into two groups, which will be called as input clustering (IC) and input-output clustering (IOC), depending on whether the output vector is also involved in the clustering process. The idea of concatenating the output vector to the input vector in the clustering process has independently been proposed by several papers in the literature although none of them presented a theoretical analysis on such procedures, but rather demonstrated their effectiveness in several applications. The main contribution of this paper is to present an approach for investigating the relationship between clustering process on input-output training samples and the mean squared output error in the context of a radial basis function network (RBFN). We may summarize our investigations in that matter as follows: (1) A weighted mean squared input-output quantization error, which is to be minimized by IOC, yields an upper bound to the mean squared output error. (2) This upper bound and consequently the output error can be made arbitrarily small (zero in the limit case) by decreasing the quantization error which can be accomplished through increasing the number of hidden units.

Thermally curable benzoxazine monomer with a photodimerizable coumarin group

Abstract: A new monomer, 4-methyl-9-p-tolyl-9,10-dihydrochromeno[8,7-e][1,3]oxazin-2(8H)-one, possessing both benzoxazine and coumarin rings in its structure was synthesized by the reaction of 4-methyl-7-hydroxycoumarin, paraformaldehyde, and p-toluidine in methanol at 40 °C and characterized with spectral analysis. Upon photolysis around 300 nm, this monomer underwent dimerization via the [2πs+2πs] cycloaddition reaction. Photodimerization reactions were investigated with UV and 1H NMR spectroscopy measurements. The thermal ring-opening reaction of the benzoxazine ring was demonstrated with differential scanning calorimetry measurements. The thermal behavior of the cured product was also investigated with thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1670–1676, 2007

Free Surface Flow In A Channel Of Large Relative Roughness

Abstract: Characteristics of free surface flow over a bed consisting of hemispherical roughness elements have been studied experimentally. Theoretical bottom of the channel has been located at a distance of 35% of the diameter below the tops of hemispheres. Usual logarithmic laws are valid for velocity distribution and friction factor as long as flow depth is large relative to roughness height. Equivalent sand roughness of the bottom is equal to 2.5 times the diameter of hemispheres. At large values of relative roughness, on the other hand, lower velocities are observed than the logarithmic law predicts, and friction factor also increases by as much as 50%. Intensity of turbulence fluctuations decreases with the increase of relative roughness. Probability density function of velocity fluctuations near the rough bed tends away from the normal distribution.