Modeling of the high-power-factor discontinuous boost rectifiers

This paper presents a modeling approach to obtain a small-signal model for a single-switch single-phase and three-phase discontinuous boost high-power-factor rectifiers. Such converters present nonlinear characteristics, and an approximation of them is used to derive the models. The most important result obtained is that the small-signal output impedance is not equal to the load impedance. The analysis is validated by experimental results     

Inactivation kinetics of food enzymes during ohmic heating

Ohmic heating of milk and fruit and vegetable juices was carried out at several incubation temperatures to investigate inactivation of alkaline phosphatase, pectin methylesterase and peroxidase. Mechanisms of inactivation of these enzymes and corresponding kinetic models were verified for each food material, using the multitemperature evaluation of inactivation data. Compared to inactivation by conventional indirect heating, kinetic parameters were changed but inactivation mechanisms remained the same. The kinetic parameter changes were relatively minor for pectin methylesterase and alkaline phosphatase. A significant destabilization of the labile isozyme fraction of peroxidase occurred by the effect of ohmic heating when the greatest decrease of stability was obtained for carrot juice.     

Adaptive memory programming for the vehicle routing problem with multiple trips

The Vehicle Routing Problem with Multiple Trips is an extension of the classical Vehicle Routing Problem in which each vehicle may perform several routes in the same planning period. In this paper, an adaptive memory algorithm to solve this problem is proposed. Computational experience is reported over a set of benchmark problem instances.     

Reversed anisotropy of grain boundary properties and its effect on grain boundary engineering

Data on anisotropy of grain boundary properties are frequently published. In some cases, when they show the reverse course of structural dependence than is expected, they can seem confusing. Examples of this “reversed anisotropy” found for grain boundary segregation, diffusion and migration are presented. We demonstrate that the reversed anisotropy of grain boundary properties is caused by the compensation effect. This can have serious consequences for grain boundary engineering. It is also suggested that grain boundaries can be classified specifically and generally solely on the basis of well-defined thermodynamic parameters.     

Experimental analysis of charge redistribution due to chemical bonding by high-resolution transmission electron microscopy

The electronic charge density distribution or the electrostatic atomic potential of a solid or molecule contains information not only on the atomic structure, but also on the electronic properties, such as the nature of the chemical bonds or the degree of ionization of atoms. However, the redistribution of charge due to chemical bonding is small compared with the total charge density, and therefore difficult to measure. Here, we demonstrate an experimental analysis of charge redistribution due to chemical bonding by means of high-resolution transmission electron microscopy (HRTEM). We analyse charge transfer on the single-atom level for nitrogen-substitution point defects in graphene, and confirm the ionicity of single-layer hexagonal boron nitride. Our combination of HRTEM experiments and first-principles electronic structure calculations opens a new way to investigate electronic configurations of point defects, other non-periodic arrangements or nanoscale objects that cannot be studied by an electron or X-ray diffraction analysis.     

A procedure for robust fitting in nonlinear regression

Outliers present more of a challenge in nonlinear than in linear models. As in the linear case, methods based on full-sample fits are not guaranteed to give larger residuals on the outliers than on inliers, and so identification methods starting from full-sample fits may fail. In addition, the fitting involves iterative calculation rather than closed-form explicit solutions, with the potential problems of convergence to local rather than global optima. The elemental set method, which has long been a fundamental tool in high breakdown linear fitting, is well suited to some nonlinear regression problems, providing an effective way of fitting the nonlinear equation, and providing the capability of doing so even in the face of large numbers of severe outliers. We discuss the basic elemental set method, and the nonlinear FAST-LTS approach, and propose a hybrid method with elemental searches preceding concentration steps.     

Generalized micropolar thermoelasticity

The basis of entropy production inequality for classical thermoelastic solid, as proposed by Green and Laws[1] and independently by Suhubi[2], is extended in this paper to encompass the more general case of micropolar thermoelastic solids. On linearisation it is shown that the energy equation becomes hyperbolic in form thereby exhibiting wave properties for thermal disturbances. As an illustrative example the propagation of acceleration waves is investigated and the acoustic tensor, which determines the speeds of propagation, is obtained.