Tikhonov Regularization of Large Linear Problems

Many numerical methods for the solution of linear ill-posed problems apply Tikhonov regularization. This paper presents a new numerical method, based on Lanczos bidiagonalization and Gauss quadrature, for Tikhonov regularization of large-scale problems. An estimate of the norm of the error in the data is assumed to be available. This allows the value of the regularization parameter to be determined by the discrepancy principle.     

Quality assessment of the a-posteriori error estimation in finite elements

The paper addresses results of numerical experimentation with an a-posteriori error estimator. The paper concentrates on the problem of the selection of benchmarks which is directed to a numerical verification of basic theoretical features of the estimator.     

Effect of cross-phase-modulation-induced polarization scattering on optical polarization mode dispersion compensation in wavelength-division-multiplexed systems

Interchannel cross-phase-modulation-induced polarization scattering (XPMIPS) and its effect on the performance of optical polarization mode dispersion (PMD) compensation in wavelength-division-multiplexed (WDM) systems are studied. The level of XPMIPS in long-haul WDM transmission systems is theoretically quantified, and its effect on optical PMD compensation is evaluated with numerical simulations. We show that in 10-Gbit/s ultra-long-haul dense WDM systems XPMIPS could reduce the PMD compensation efficiency by 50%, whereas for 40-Gbit/s systems the effect of XPMIPS is smaller.     

Preparation and characterization of alpha,alpha'-bisdiarylamino-capped oligothiophenes

[reaction: see text] A series of alpha,alpha'-bisdiarylamino-capped oligothiophenes C(n) were prepared by the palladium-catalyzed reaction of the dibromo compounds A(i) with diarylamines, N,N-diarylamino-substituted thiophenes or 2,2'-bithiophenes BX(j). These easily oxidizable compounds exhibit a high tendency to form amorphous glasses and characteristic electrochemical and spectroscopic properties that depend significantly on the number of their thiophene moieties.     

Hyperbolic Spirals as Surface Structures in Thin Layers

When thin layers of 4-chloro-3-methylphenol and a copolymer of methyl(methacrylate) and maleic acid dissolved in acetone are dried by solvent evaporation, various surface structures appear. Besides linear surface deformations that can ramify like fractals, spirals of the hyperbolic type have been found. The surface structures are due to crystallization processes and flows caused by surface tension differences. The spirals are surface elevations with grooves on both sides as shown by surface profile measurements by means of a microscope interferometer. The addition of surfactants reduces the structure formation. A large surfactant concentration prevents the structure formation. Copyright 2001 Academic Press.