Design of a PID-like compound fuzzy logic controller

The paper describes a novel method for the design of a fuzzy logic controller (FLC) with near-optimal performance for a variety of operating conditions. The approach is based on the analysis of the system behaviour in the error state-space. The final control structure, in a form of a compound FLC, is arrived at in two stages. The first stage encompasses design and tuning of a PID-like fuzzy controller. The second stage consists of placing an additional fuzzy controller, of a structure similar to that of the first one, in parallel with the PID-like fuzzy controller designed in the first stage. The resulting compound controller is characterised with high performance in the wide range of operating conditions, and with small number of parameters that can be adjusted using simple optimisation methods. The controller is developed and tested for a plant comprising a vector controlled induction motor drive.     

Control Algorithm for the Inverter Fed Induction Motor Drive with DC Current Feedback Loop Based on Principles of the Vector Control

ABSTRACT

This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.     

Robust M-periodogram with dichotomous search

The problem of sinusoidal frequency estimation in heavy-tailed noise environment is addressed. A method based on the robust M-periodogram is proposed. Specifically, a suboptimal coarse frequency estimate provided by the robust M-periodogram is improved using the modified dichotomous search. Simulations that consider most common heavy-tailed noise models demonstrate that the proposed method outperforms several recently proposed methods. The method can be readily extended to deal with multiple sinusoids.     

Iron at the Interface of Hepatocellular Carcinoma

Cancer incidence and mortality are rapidly growing, with liver cancer being the sixth most diagnosed cancer worldwide and the third leading cause of cancer death in 2020. A number of risk factors have been identified that trigger the progression to hepatocellular carcinoma. In this review, we focus on iron as a potential risk factor for liver carcinogenesis. Molecules involved in the regulation of iron metabolism are often upregulated in cancer cells, in order to provide a supply of this essential trace element for all stages of tumor development, survival, proliferation, and metastasis. Thus, cellular and systemic iron levels must be tightly regulated to prevent or delay liver cancer progression. Disorders associated with dysregulated iron metabolism are characterized with increased susceptibility to hepatocellular carcinoma. This review discusses the association of iron with metabolic disorders such as hereditary hemochromatosis, non-alcoholic fatty liver disease, obesity, and type 2 diabetes, in the background of hepatocellular carcinoma.     

An Operational Model for Support of Integrated Watershed Management

This paper presents a computer simulation-based methodology for operational support of integrated water resources management. The methodology is based on the systems approach, and use of feedback to capture physical and socio-economic processes occurring within a watershed. The approach integrates well established simulation models of physical processes with simulation models that describe socio-economic processes. The proposed methodology is illustrated by the evaluation of risk and vulnerability to changing climatic and socio-economic conditions in the Upper Thames watershed (south-western Ontario, Canada).The model results indicate that flooding in the watershed will be more severe as a result of climate change, while low flows are expected to remain at their current level. The most significant socio-economic factor in the Upper Thames watershed is water availability, shown to become under climate change a limiting factor for future growth and development.     

Simulation of Transcritical Flow in Pipe/Channel Networks

Using finite difference methods in conjunction with the reduced momentum equation and applying boundary condition structure inherent to subcritical flow to all regimes, is an approach that enables efficient numerical simulation of supercritical and transcritical flows in pipe/channel systems. However, as well as certain errors within a single channel due to incomplete equations, this technique also may introduce unwanted effects propagating across a network in both upstream and downstream directions. These may include: unrealistic backwater effects due to improper boundary conditions, nonamplifying oscillations due to jerky jump movement, and other computational instabilities. Practical implications of these are analyzed in detail and are illustrated using a set of examples. Sensitivity analyzes and comparisons with analytical solutions and laboratory experiments are made. The measures to reduce the inaccuracies inevitable in simulation of transcritical flows are discussed.     

A study of pyrolysis of phenolic resin reinforced with carbon fibres and oxidized pan fibres

Pyrolysis of composites prepared from a phenol-formaldehyde resin and carbon fibres (CFRC) or oxidized PAN fibres (OFRC) has been investigated up to 1270 K. Two temperature regions can be distinguished in the pyrolysis of the CFRC: below 770 K the carbon fibres hold the composite structure resisting the tendency of the resin to produce composite shrinkage; above 770 K the CFRC volume and porosity abruptly increase due to a weakening of fibre/resin adhesion. During the pyrolysis of the OFRC a chemical reaction at the fibre/resin interface apparently takes place, beginning at 570 K and producing important changes in the material at 870–970 K. Somewhat smaller weight losses and markedly lesser shrinkage of the pyrolysed composite with respect to its separately treated components have been found. The fibres and the resin coalesce into a product having relatively high density and low porosity, the latter mainly consisting of narrow pores. Hydrogen content of the product is lower than that of the separately treated constituents. The reflections of both the resin and the oxidized PAN fibres are seen only in the X-ray patterns of the OFRC treated at low temperature, but above 670 K only the reflection due to the fibres appears. The interlayer spacing of the fibres in the composite is greater than in the fibres alone treated under the same conditions. According to the IR spectra, the CN groups and aromatic CH groups disappear from the composite at lower temperature than from its components treated separately.The existence of the reaction between the resin and the oxidized PAN fibres, leading to the destruction of the fibre materials, means that the co-carbonization product at 1270 K is not a composite and will not have the necessary mechanical properties. Therefore, this study must continue to look for fibres and matrices which are compatible during co-carbonization to 1270 K.     

A decomposition method for the solution of the network equations of short-term dynamics of connected power systems,taking into consideration the axial asymmetry of the machines

In the numerical simulation of the short-term dynamics of power systems, mutual angles of machine rotors and other relevant state variables are observed for a period up to a few seconds after sudden and forced switching on and tripping of the machines, transmission lines, transformers and consumer buses. On the one hand the set of differential equations, which are associated with the machines, is numerically integrated, and on the other the set of algebraic equations, which are associated with the network, is solved. This paper presents a decomposition method for solving the network equations of short-term dynamics of connected power systems, taking into consideration the axial asymmetry of the machines.     

Refined fourier-transform method of analysis of full two-dimensional digitized interferograms

A refined Fourier-transform method of analysis of interference patterns is presented. The refinements include a method of automatic background subtraction and a way of treating the problem of heterodyning. The method proves particularly useful for analysis of long sequences of interferograms.