Analogue-to-digital armature current transducer for chopper-fed DC motor drives

A transducer scheme is suggested, permitting A/D conversion of the armature current for microcomputer-controlled variable-frequency-chopper-fed DC motor drives. The transducer supplies the information about the average between two thyristor triggerings value of the armature current, independent of the frequency of the current.     

GROUP DECISION-MAKING WITH A FUZZY MAJORITY VIA LINGUISTIC QUANTIFIERS. PART II: A COMPETITIVE-LIKE POOLING

Abstract

Starting from individual fuzzy preference relations, some (sets of) socially best acceptable options are determined, directly or via a social fuzzy preference relation. An assumed fuzzy majority rule is given by a fuzzy linguistic quantifier, e.g., “most.” Here, as opposed to Part I, where we used a consensory-like pooling of individual opinions, we use an approach to linguistic quantifiers that leads to a competitive-like pooling. Some solution concepts are considered: cores, minimax (opposition) sets, consensus winners, and so forth,     

Optimizing a random access system by biased source blocking

The paper considers the theoretical problems associated with control of a random access system. The dynamic flow model of a simple pure-Aloha multiple access scheme is described first, which serves as a basis for the consideration of catastrophic system behaviour in the parameter space. Then the design of the optimal control system using the Pontryagin theory is discussed. As a result of those considerations the theoretical requirements for optimizing the system operation are formulated. Finally, the control scheme of ICP-type which complies with those requirements is presented.     

Generalization of discounted multistage decision making and control through fuzzy linguistic quantifiers: an attempt to introduce commonsense knowledge

This paper is an extension of work published by Kacprzyk in 1983 in which, by using a fuzzy-logic-based calculus of linguistically quantified propositions, some generalizations of multistage decision making and control have been proposed. Namely, a new class of models has been developed that make it possible, roughly speaking, to find an optimal sequence of controls best satisfying (fuzzy) constraints and goals at, say, most (or any other suitable linguistic quantifier, for example ‘almost all’, ‘at least a few’) of the control stages. In this paper we further extend the above-mentioned approach by introducing discounting (a variable importance of particular control stages, in principle ‘the earlier the more important’). We propose a new model that can find an optimal sequence of controls best satisfying the (fuzzy) constraints and goals at, say, most of the earlier control stages. We employ a fuzzy-logic-based calculus of linguistically quantified propositions and develop a branch-and-bound algorithm for solving the problem. The approach may be viewed as an attempt to introduce commonsense knowledge, in its fuzzy-disposition-based representation due to Zadeh, into multistage decision making and control models.     

EFFECT OF FINISH-FRYING CONDITIONS ON THE QUALITY OF FRENCH FRIED POTATOES

Limpness, rigidity and moisture content of French fried potatoes, shoes-string style, depend on the distribution of moisture within the strips and are not directly related to the temperature of samples before finish frying. When samples are finish fried from the thawed state, the limpness and rigidity of the finished product are not significantly different than in samples fried from the frozen state, but considerable clustering, adherence of units to each other, is observed. Partial thawing or refreezing of samples before finish frying may result in the nonuniform distribution of moisture within the strips and decrease rigidity and increase limpness of the finished product. The optimum quality of the finished product in respect to limpness and color was obtained in samples fried for 2.75 min at 360°F. The level of solids in the par-fried state within the range of 28–38% does not have an apparent effect on the quality of the finished product. The limpness and rigidity factors of samples deteriorate after finish-frying, and this process is accelerated by exposure to infrared heat lamps. The susceptibility of samples to infrared heat and the rate of the increase in limpness depend on the quality of the raw potatoes and the quality of the outer crust of the units.     

Microstructure characterization of advanced protective Cr/CrN+a‐C:H/a‐C:H:Cr multilayer coatings on carbon fibre composite (CFC)

Studies of advanced protective chromium‐based coatings on the carbon fibre composite (CFC) were performed. Multidisciplinary examinations were carried out comprising: microstructure transmission electron microscopy (TEM, HREM) studies, micromechanical analysis and wear resistance. Coatings were prepared using a magnetron sputtering technique with application of high‐purity chromium and carbon (graphite) targets deposited on the CFC substrate. Selection of the CFC for surface modification in respect to irregularities on the surface making the CFC surface more smooth was performed. Deposited coatings consisted of two parts. The inner part was responsible for the residual stress compensation and cracking initiation as well as resistance at elevated temperatures occurring namely during surgical tools sterilization process. The outer part was responsible for wear resistance properties and biocompatibility. Experimental studies revealed that irregularities on the substrate surface had a negative influence on the crystallites growth direction. Chromium implanted into the a‐C:H structure reacted with carbon forming the cubic nanocrystal chromium carbides of the Cr₂₃C₆ type. The cracking was initiated at the coating/substrate interface and the energy of brittle cracking was reduced because of the plastic deformation at each Cr interlayer interface. The wear mechanism and cracking process was described in micro‐ and nanoscale by means of transmission electron microscope studies. Examined materials of coated CFC type would find applications in advanced surgical tools.     

DYE RECOVERY BY LOW PRESSURE ULTRAFILTRATION†

Ultrafiltration or textile dyes using polyacrylonitrile hollow fibers is reported. Experiments were carried out in recirculating system with various flow intensities along the fiber. Dependence of rejection and membrane flux on concentration of bulk solution is presented. Due to aggregation of dye particles and good separation characteristics of membranes used high water recovery and concentration of dyes were obtained.     

Model-based process redesign

A method is presented for the model-based redesign of enterprises. It consists of two main steps, the initialization step and the optimization step. During the initialization step, the processes are modelled and analysed. During the optimization step, the optimal configuration is found for the possible modifications of the processes. Emphasis is placed on the process analysis. The proposed approach is based on activity chains which describe the set of activities needed for the achievement of a given goal, and their execution order necessary to guarantee a low processing time. An algorithm is presented for filtering such activity chains from an enterprise model. It is based on graph theory and corresponds to the solution of an optimization problem, whereby the sum of weights of all edges belonging to the solution graph should be maximized under some given constraints. Because of the high complexity of the problem, some complexity-reducing measures are presented, measures that arise from the earlier problem analysis.     

THE EFFECT OF PRETREATMENT OF SHREDDED CELERIAC USING SOLUTIONS OF ENZYMATIC BROWNING INHIBITORS ON THE QUALITY OF MINIMALLY PROCESSED PRODUCT

ABSTRACT

The study investigated the effect of soaking celeriac flakes in solutions containing various concentrations of enzymatic browning inhibitors on the quality of stored minimally processed product. Ascorbic acid (0.2–0.5%), 4‐hexylresorcinol (0.003–0.01%), sodium chloride (0.1–0.5%) and sodium lactate (2–3%) were used as browning inhibitors. On the basis of the conducted tests, it was found that among the applied browning inhibitors, only ascorbic acid had an advantageous effect on the quality of stored celeriac flakes. Along with an increase in its concentration in the solution (0.2–0.5%) used for the pretreatment of the flakes, the value of color parameter a* decreased, while the value of parameter b* increased. At the concentration of ascorbic acid in the solution exceeding 0.25%, flake color in the sensory examination was evaluated as desirable. An increase of ascorbic acid concentration in the solution in the range from 0.2 to 0.4% resulted in a decrease in the total mesophilic and psychrophilic bacteria counts, respectively, by 3 and 1 log cfu/g of the stored product.

PRACTICAL APPLICATIONS

Minimal processing of celeriac provides convenience for consumers and many economic benefits for producers. Minimal processing of celeriac can induce disadvantageous changes in tissue, which may lead to darkening of the flakes and deterioration of product sensory attributes. Moreover, shredded raw material constitutes an excellent medium for the development of microorganisms. This article contains information about the effectiveness of enzymatic browning inhibitors for extending the shelf life of celeriac flakes. We show a range of concentrations of inhibitors, which improve the preservation of color, intrinsic taste and microbial quality of minimally processed celeriac.