Coal analysis by application of the partial least squares method to infrared spectra

Summary A method for the rapid characterization of brown coals based on the application of a powerful method of principal component analysis, the Partial Least Squares method (PLS), is described. A data catalogue of 44 brown coals from different deposits of East European and Asian countries was used, which lists analyses of several coal parameters. Infrared spectra of brown coals were recorded and different coal properties were predicted with the help of PLS. The results show that, with the PLS-method used, several coal properties can be predicted and it is possible to describe the classification of a coal for several technological processes. The developed method is useful because of the multiplicity of information obtained within a short time and because it is possible to replace lengthy classical methods.     

On two problems related to cancellativity

Two decision problems that are related to the properties of right-cancellativity and left-cancellativity, respectively, of the monoidm _T defined by a presentation (Σ;T), are investigated. It is shown that these problems are undecidable in general. In fact, they remain undecidable, even when they are restricted to presentations involving finite Church-Rosser Thue systems. On the other hand, if only finite presentations involving monadic Church-Rosser Thue systems are considered, then these two problems become decidable in polynomial space.     

Quasi-Self-Preserving Log-Normal Size Distributions in the Transition Regime

A log-normal model, based on the extended SIMPLER-algorithm utilizing the Modal Aerosol Dynamics Modelling Technique, and a sectional model are compared for Brownian coagulation in the transition regime. The models are in good agreement with respect to the calculated particle size distribution moments. Applying the log-normal model a simple coagulation model consisting of a closed set of five equations is developed that does not require the solution of ordinary diferential equations.     

Computational Experience with Ill-Posed Problems in Semidefinite Programming

Many theoretical and algorithmic results in semidefinite programming are based on the assumption that Slater's constraint qualification is satisfied for the primal and the associated dual problem. We consider semidefinite problems with zero duality gap for which Slater's condition fails for at least one of the primal and dual problem. We propose a numerically reasonable way of dealing with such semidefinite programs. The new method is based on a standard search direction with damped Newton steps towards primal and dual feasibility.     

ZnO homoepitaxy on the O polar face of hydrothermal and melt-grown substrates by pulsed laser deposition

2 cm diameter hydrothermal ZnO crystals were grown and then made into substrates using both mechanical and chemical-mechanical polishing (CMP). CMP polishing showed superior results with an (0002) Ω scan full width half maximum (FWHM) of 67 arcsec and an root mean square (RMS) roughness of 2 Å. In comparison, commercial melt-grown substrates exhibited broader X-ray diffraction (XRD) linewidths with evidence of sub-surface crystal damage due to polishing, including a downward shift of c-lattice parameter. Secondary ion mass spectroscopy revealed strong Li, Fe, Co, Al and Si contamination in the hydrothermal crystals as opposed to the melt-grown substrates, for which glow discharge mass spectroscopy studies had reported high levels of Pb, Fe, Cd and Si. Low temperature photoluminescence (PL) studies indicated that the hydrothermal crystal had high defect and/or impurity concentrations compared with the melt-grown substrate. The dominant bound exciton for the melt-grown substrate was indexed to Al. ZnO films were grown using pulsed laser deposition. The melt-grown substrates gave superior results with XRD (0002) Ω and 2θ/Ω WHM of 124 and 34 arcsec, respectively. Atomic force microscope measurements indicated a low RMS roughness (1.9 nm) as confirmed by fringes in the XRD 2θ/Ω scan. It was suggested that the improvement in XRD response relative to the substrate might be due to “healing” of sub-surface polishing damage due to the elevated T_s used for the growth. Indeed the c-lattice parameter for the homoepitaxial layer on the melt-grown substrate had become that which would be expected for strain-free ZnO. Furthermore, the stability of the PL peak positions relative to bulk ZnO, confirmed that the films appear practically strain free.