Quasilinearized Regression

Estimation in nonlinear regression usually requires a considerable amount of computational work. If it is possible to linearize the original formulas, the linear regression is sometimes applied to transformed linear relations. The method of quasilinearized regression (first order approximation of nonlinear regression), comparable to linear regression, with respect to computational effort, is described in this paper. This method gives substantially better results than linear regression of linearized formula.     

The Effect of Implanted Al and/or Y on the Scale Formation on Low-Al Fe20Cr2Al Alloy

The very early stages of the oxidation of an Fe20Cr2Al alloy, unmodified and ion-implanted by aluminium, yttrium and a combination of both elements, Al and Y, were studied at 1100 °C in oxygen using two-stage-oxidation exposures with ¹⁸O₂ as a tracer and subsequent characterisation of the scales using SIMS analyses of distribution of oxygen isotopes and oxide-related negative ion clusters, SEM observations of the surface morphology and photoluminescence spectroscopy analysis of the phase composition. The scales formed in all cases, except for the Al-implanted alloy, exhibited layered structures, with the outer part comprising Fe- and Cr-rich oxide, and the inner part being Al₂O₃, which grew due to a mixed outward–inward mechanism . The alumina sub-layers contained the transient oxides and α-Al₂O₃. Implanted Al significantly affected the mechanism of the scale growth, providing that the scale consisted essentially of α-Al₂O₃, and grew via a mixed inward-outward mechanism typical for scales on alumina formers.     

Practical assessment of the nature of business processes

Information Systems and e-Business Management - The aim of the article is to present a framework enabling the quick and practical assessment of the nature of business processes, necessary to select...     

Power system stability enhancement by WAMS-based supplementary control of multi-terminal HVDC networks

This paper deals with supplementary control of a MTDC network designed for the stability enhancement of a AC power system. The proposed control is a WAMS-based control modulating the real and reactive power at the terminals of the DC network. Relevant control formulas have been derived for a linear multi-machine system model with the application of the direct Lyapunov method. Validity and robustness of the proposed control has been verified by computer simulation for a multi-machine test system using a nonlinear model and detailed modeling of power system components. The proposed control is robust and insensitive to changes in the network configuration and loading conditions in the AC power system. In the case, when more of the MTDC networks and/or the HVDC links are used in one interconnected power system the proposed stabilizing control produces additive damping i.e. each controlled network element contributes to the positive damping. Some practical aspects have also been discussed. The proposed WAMS-based stabilizing control of the MTDC network is innovative by both its main concept and the derivation of control formulas using the direct Lyapunov method.     

Characterization of Ceramic Foam Filters Used for Liquid Metal Filtration

In the current study, the morphology including tortuosity, and the permeability of 50-mm thick commercially available 30, 40, 50, and 80 pores per inch (PPI) alumina ceramic foam filters (CFFs) have been investigated. Measurements have been taken of cell (pore), window, and strut sizes, porosity, tortuosity, and liquid permeability. Water velocities from ~0.015 to 0.77 m/s have been used to derive both first-order (Darcy) and second-order (Non-Darcy) terms for being used with the Forchheimer equation. Measurements were made using 49-mm “straight through” and 101-mm diameter “expanding flow field” designs. Results from the two designs are compared with calculations made using COMSOL 4.2a^® 2D axial symmetric finite element modeling (FEM), as a function of velocity and filter PPI. Permeability results are correlated using directly measurable parameters and compared with the previously published results. Development of improved wall sealing (49 mm) and elimination of wall effects (101 mm) have led to a high level of agreement between experimental, analytic, and FEM methods (±0 to 7 pct on predicted pressure drop) for both types of experiments. Tortuosity has been determined by two inductive methods, one using cold-solidified samples at 60 kHz and the other using liquid metal at 50 Hz, giving comparable results.