Multi-machine operations modelled and controlled as switched linear repetitive processes

Many industrial processes involve the processing of a single workpiece by successively passing it through a sequence of machines. The most common example is metal rolling where the metal strip of finite length is shaped by passing it through different sets of rolls and the output from one forms the input to the next and so on. In this paper, we develop a new approach to the analysis and overall control of such systems by first modelling them as a linear repetitive process with switched dynamics. The end result is control law design algorithms which can be implemented using LMI based computations.     

Physical neuroergonomics: The human brain in control of physical work activities

One of the important functions of the human brain is voluntary control of movements and motor activities combined with perceptual, cognitive and affective processes. This paper introduces the emerging field of study, named hereby as physical neuroergonomics, that focuses on the knowledge of human brain activities in relation to the control and design of physical tasks. Motor, cognitive and emotional aspects and their inter-relationships in connection to physical ergonomics are considered. A review of recent advances in functional electroencephalography (EEG), with special accent on the time domain analyses of the human brain activity in selected motor tasks, is also presented. The reported studies of isometric elbow-flexion contractions confirmed that the cerebral-cortex system controls the extent of muscle activation and is responsible for smoothing out high-speed motor control processes. Furthermore, the emotional attitudes of the subject to the activity can compel performance beyond acceptable loading through psychological pressure or necessity. The discussed results are important to one's understanding of human limitations and capabilities on a variety of physical tasks, and may ultimately help explain the mechanisms of musculoskeletal injuries at work. These results also underscore the need for a novel approach to workplace studies, i.e. neuroergonomics design.     

New perylene dyes,derivatives of 1,6,7,12‐tetrachloroperylene‐3,4,9,10‐tetracarboxylic acid: synthesis and application

New dyes – aliphatic esters of 1,6,7,12‐tetrachloroperylene‐3,4,9,10‐tetracarboxylic acid – were prepared as potential fluorescent light‐stable colorants for high‐visibility safety wear. The structure of the 15 perylenes was confirmed by ¹H and ¹³C nuclear magnetic resonance spectroscopy and mass spectrometry, and their spectroscopic and physicochemical properties were determined. An attempt was made to apply the synthesised products as disperse dyes in the coloration of polyester as well as in the mass coloration of polystyrene and poly(methyl methacrylate). The light, wash, and rubbing fastness of the dyeings were determined, and chromaticity coordinates of selected samples were measured and discussed.     

Mechanism of swelling and extraction and coal structure

An attempt is made to develop a comprehensive model of coal structure based on results of various experiments involving extraction and swelling of a coal by solvents. These are described in terms of electron-donor and electron-acceptor characteristics, of mass spectrometric analysis of coal extracts, of pulse ¹H n.m.r. measurements of mobilities of coal components, porosity measurements. The theory of coal swelling cannot be adapted from the theory of polymer swelling.     

Numerical calculations of the influence of large earth currents on a buried cable

In certain applications one needs to determine the potential generated in the electrical cable by the earth current and leakage currents. In this paper a simple numerical method to solve this problem is considered. The results of the numerical experiments indicate that the proposed scheme is highly accurate.     

Characteristics of a double-orifice nebulizer

Aerosol generation in a pneumatic nebulizer with a double-orifice nozzle was studied in the particle size range of 0.8–10 μm. It was found that the aerosol generation rate can be changed without significant changes in the aerosol size distribution by changing the distance between the orifices. The aerosol size distribution was modified by changing the input air pressure. A Wright type nebulizer was modified to produce a wider spectrum of particles.     

Synthesis and characterization of nanostructured carbons with controlled porosity prepared from sulfonated divinylbiphenyl copolymers

A series of porous carbons have been prepared by the carbonization of spherical porous sulfonated divinylbiphenyl (DVBPh) copolymers. Carbons in spherical bead form were obtained by the pyrolysis of H⁺, Na⁺, Cs⁺, Cu²⁺, Co²⁺ and Fe³⁺ forms of the sulfonated DVBPh beads. Thermogravimetric analysis (TGA) in an inert nitrogen atmosphere (25-900 °C) was carried out on the DVBPh copolymer precursor, the sulfonated copolymer sample and various ionic forms of the resin. The TGA data provides evidence that the sulfonation process thermally stabilized the polymer resulting in a higher final carbon yield. It was found that the pyrolysis yield was ca. 40% for the sulfonic acid derivative and between 40% and 65% for the various sulfonic acid salts. The highest yield was observed for the monovalent sodium and cesium ionic forms of the sulfonated DVBPh copolymers. Low temperature nitrogen adsorption/desorption isotherms provided information on the porous structure of the polymer precursors and the carbons prepared from them. The pore structure in the carbons was found to a large extent to be similar to the porous structure of the starting sulfonated resin material, however, the metal form was found to impact on the micropore structure of the resulting carbons. The carbon materials prepared were characterized by X-ray photoelectron spectroscopy (XPS) to provide information on the form of the residual sulfur in the carbons. XPS results suggest that the ionic form of the sulfonic resin influences the amount and the form of the sulfur and this may be correlated with the yield of the final carbon.     

The quadratic electrooptic effect and estimation of antipolarization in ADP

The quadratic electrooptic coefficients g₁₁₁₁ and g₂₂₁₁ have been measured interferometrically in ADP at room temperature. In addition, ‖g₁₁₁₁-g₂₂₁₁‖ was determined by a dynamic polarimetric technique at the same temperature. Both experiments yield values for g₁₁₁₁-g₂₂₁₁ at 21 C and λ = 0.633 μm with an average of (-5.9±0.5)×10^-20 m²/V². An estimate is made, using this value, of the spontaneous antipolarization appearing in the antiferroelectric phase of ADP. This antipolarization is found to be comparable in magnitude with the spontaneous polarizations observed in ferroelectrics belonging to the KDP family of crystals.     

Nanoarchitectonics: Complexes and Conjugates of Platinum Drugs with Silicon Containing Nanocarriers. An Overview

The development in the area of novel anticancer prodrugs (conjugates and complexes) has attracted growing attention from many research groups. The dangerous side effects of currently used anticancer drugs, including cisplatin and other platinum based drugs, as well their systemic toxicity is a driving force for intensive search and presents a safer way in delivery platform of active molecules. Silicon based nanocarriers play an important role in achieving the goal of synthesis of the more effective prodrugs. It is worth to underline that silicon based platform including silica and silsesquioxane nanocarriers offers higher stability, biocompatibility of such the materials and pro-longed release of active platinum drugs. Silicon nanomaterials themselves are well-known for improving drug delivery, being themselves non-toxic, and versatile, and tailored surface chemistry. This review summarizes the current state-of-the-art within constructs of silicon-containing nano-carriers conjugated and complexed with platinum based drugs. Contrary to a number of other reviews, it stresses the role of nano-chemistry as a primary tool in the development of novel prodrugs.     

Strain localization and superplastic-like flow in copper at high temperature

The localization of plastic deformation at high temperature and its influence on the mechanical performance of polycrystalline copper were studied. The results showed that the instability of the load during high-temperature deformation is caused by the localization of plastic flow within shear bands. This in turn leads to heterogeneity of the dislocation structure and becomes a motive for selective static recrystallization along shear bands. Under appropriate conditions the balance between the formation of new shear bands and recrystallization (or recovery) within already inactive shear bands leads on a global scale to superplastic-like behaviour of the metal.