Showing papers by "University of Bath published in 1984"

Multiple-Valued Logic—its Status and its Future

Abstract: Multiple-valued logic, in which the number of discrete logic levels is not confined to two, has been the subject of much research over many years. The practical objective of this work has been to increase the information content of the digital signals in a system to a higher value than that provided by binary operation. In this tutorial/survey paper we will review the historical developments in this field, both in circuit realizations and in methods of handling multiple-valued design data, and consider the present state-of-the-art and future expectations.

The extraction of ionic conductivities and hopping rates from a.c. conductivity data

Abstract: Over a wide range of frequencies, the a.c. conductivity of ionic materials shows two regions of frequency-dependent conductivity. These are each characterized by a term Kω p 1− ω n where K, n are constants, ω p is a fundamental frequency identified with the hopping rate and ω is the measuring frequency. This behaviour is an example of Jonscher's Law of Dielectric Response for ionic conductors. In many cases, the region of low-frequency dispersion approximates to a frequency-independent plateau which may be taken as the d.c. conductivity. In others, a significant low-frequency dispersion is present and cannot be ignored in determining the effective d.c. conductivity. A method for the extraction of d.c. conductivities, hopping rates and for estimating carrier concentration effects is described. Data for three different types of material, single-crystal LiGaO2, β″-alumina and Na/Ag β-alumina are used to illustrate the method.

A classification and review of models of the intra-firm innovation process

Abstract: The recognised complexity of the innovation process not only makes it difficult to manage, explain and study, but also presents problems for the development of a generalised model. Cooper's recent article in ‘R&D Management’ suggests that the construction of a generalised model is inappropriate because there appear to be a number of different types of innovation processes. However, many of the studies of innovation postulate or assume a general model which represents the stages involved in the firm. This paper reviews the models of the innovation process which have been proposed and the author classifies them according to his taxonomy of different types: (a) Departmental-stage models (b) Activity-stage models (c) Decision-stage models (d) Conversion process models (e) Response models The advantages and disadvantages of each approach are discussed and the conclusion reached is that still more research needs to be concentrated on the nature of the innovation process within the firm itself. The absence of a definitive model compounds the problems of semantics and definitions when discussing innovation.

The Impact of Organizational Culture on Approaches to Organizational Problem-Solving

Abstract: This paper shows how organizational culture can act as an obstacle to change and problem resolution. The introduction describes how the author's interest in 'problem cultures' arose, and the next two sections attempt to define and refine the definition and methodology of organizational culture. The main section summarizes the problematical characteristics of those cultures studied: six cultural orientations are identified and their effects examined. A number of issues are then discussed: by what process does culture shape behaviour? What evidence is there for the wider existence of the cultural orientations described? A 'universal-variable' thesis or organizational culture is put forward, and the concluding remarks seek to establish a relationship between organizational culture and orientations to change.

The elastic behaviour of TeO2 glass under uniaxial and hydrostatic pressure

Abstract: TeO2 glass of purity exceeding 98.5 mol.% has been made, despite earlier suggestions that some 7.5–10 mol.% of modifier is required to form vitreous telluride networks. It is argued that in view of the high purity of the glass obtained, TeO2 may well be able to form glass by itself, given an appropriate thermal history in preparation. The hydrostatic and uniaxial pressure dependences of ultrasonic waves propagated in this glass at room temperature have been measured. The results provide the second and third order elastic constants of the glass. The bulk modulus is consistent with a ring diameter averaging about 8 atoms (Te4O4 rings) suggesting that the glass is a disordered version of paratellurite; however, if the TeO bending force constant were to be unusually strong, then a larger ring diameter (as in tellurite) would be indicated. Although the anion coordination number is only 4, the pressure derivatives of the second order elastic constants are positive and the third order elastic constants are negative, in marked contrast to the anomalous behaviour of silica-based glasses. These findings suggest that bond bending motions of bridging atoms between the trigonal bypyramidal groups (which are the structural units) do not play an important role in the elastic properties of TeO2 glass. In consequence the shear and oongitudinal acoustic mode Gruneisen parameters are both positive (γ1 = +2.14, γs = +1.11): the long wavelength acoustic modes stiffen under hydrostatic pressure.

Phase-Locked Transparent Tone-in-Band (TTIB): A New Spectrum Configuration Particularly Suited to the Transmission of Data Over SSB Mobile Radio Networks

Abstract: The paper describes a new pilot tone SSB configuration, transparent tone-in-band (TTIB), which may be used in mobile radio systems from low-band VHF to microwave frequencies. By utilizing audio signal processing techniques in the transmitter and receiver, the pilot reference tone may be positioned centrally within the RF channel bandwidth without losing the property of data transparency and also retains the many system advantages of tone-in-band SSB over the pilot carrier and tone-above-band schemes. Besides speech transmissions, results are presented for noncoherent FSK and DPSK data formats under white noise and Rayleigh fading conditions. Finally, a new technique utilizing TTIB is suggested to facilitate the use of coherent data systems.

Ethylene-Independent and Ethylene-Dependent Biochemical Changes in Ripening Tomatoes

Abstract: Fruits of Lycopersicon esculentum Mill cv Sonatine stored in 6% CO 2 , 6% O 2 , and 88% N 2 for 14 weeks at 12°C, exhibited a temporal separation of certain biochemical events associated with ripening. The specific activity of two citric acid cycle enzymes, citrate synthase and malate dehydrogenase, fell substantially during the first 2 weeks of storage when changes in organic acid concentration also occurred. During this period, lycopene, polygalacturonase, and ethylene were undetectable. When fruit were removed from store, ethylene was evolved and polygalacturonase and invertase activity were rapidly initiated as was synthesis of lycopene. To determine whether the changes in organic acid metabolism were affected by ethylene, fruit was kept at 22°C in either a normal atmosphere or a normal atmosphere supplemented with 27 microliters per liter of ethylene, and it was shown that in both atmospheres similar quantitative changes to those described above occurred in the citric acid cycle enzymes specific activities before any detectable increase in the specific activities of invertase and polygalacturonase. These latter changes, together with pigment changes, occurred between 2 and 3 days earlier in fruit exposed to ethylene, compared with those kept in a normal atmosphere.

Using Repertory Grids for Problem Construction

Abstract: In the last couple of years, O.R. workers have expressed interest in the use of repertory grids as a part of their armoury for tackling messy problems in organizations. This paper is designed to describe some of our experiences of using grids to aid the process of problem construction. It will also express some of our views of the theoretical and technical aspects of their use for working on problems. The principles behind the use of grids invite the design of other methods for managing qualitative problem data. The paper will briefly introduce some we have found helpful.

The environmental fatigue behaviour of reinforced plastics

Abstract: This paper presents the results of an investigation of the effects of hygrothermal conditioning on the mechanical properties and fatigue behaviour of epoxy-based composites reinforced with carbon, glass and aromatic polyamide fibres. Cross-plied (0$^\circ$/90$^\circ$) laminates of these materials, of nominal fibre volume fraction ca. 0.6, were conditioned by drying, by exposing to a 65% r.h. (relative humidity) atmosphere and by boiling in water. The effects of these treatments on the tensile and shear strengths and on the tensile fatigue response of the laminates when tested orthogonally and at $\pm$ 45$^\circ$ to the fibre lay-up are discussed. The 0$^\circ$/90$^\circ$ tensile properties of the three laminates are relatively little affected by the conditioning treatments except for g.r.p. (glass reinforced plastic) exposed to boiling water, and of K.f.r.p. (Kevlar fibre reinforced plastic) in which the strength is reduced somewhat by complete drying. The shear strengths and $\pm$45$^\circ$ tensile strengths are more sensitive to the effects of moisture, however, and it appears that optimum strengths are developed after conditioning at the intermediate 65% r.h. Tensile fatigue tests have been carried out on laminates in the 0$^\circ$/90$^\circ$ and $\pm$45$^\circ$ orientations. In c.f.r.p. (carbon fibre reinforced plastic) there is no effect of conditioning on the fatigue behaviour of 0$^\circ$/90$^\circ$ samples, and in g.r.p. only the boiling water treatment affects the results. Preloading g.r.p. samples before conditioning has no effect on their fatigue behaviour. The tensile fatigue resistance of 0$^\circ$/90$^\circ$ Kevlar-epoxy laminates is reduced by drying more than by boiling, and in all conditions the stress against logarithm of life curves are characterized by a downward curvature that renders the long term stability of this material suspect. This behaviour is also reflected in differences in the $\pm$45$^\circ$ tensile fatigue response of the three laminates.

The Mathematical Modelling of Hydrostatic Pumps and Motors

Abstract: Accurate mathematical models of hydrostatic pumps and motors are required in the synthesis and analysis of hydraulic systems. Increasingly the models are used in computer simulation work where the performance of the machines must be represented over a wide range of operating conditions.Examination of test data has shown significant differences in the real performance characteristics of hydrostatic machines compared to the characteristics predicted by classical models based on simple linear theory. This paper describes these differences and shows the way that the characteristics can change with different designs of machine.A mathematical model is developed which may be adapted to describe the wide range of characteristics associated with the different designs. This model has shown good agreement with test data.Recommendations are made for more comprehensive performance tests to provide the data required for more accurate models.

Cuticle, shell porosity and water uptake through hens’ eggshells

Abstract: 1. There was no correlation between water uptake by a warm egg (37 °C) immersed in iced water and the shell's porosity as measured by water vapour conductance. 2. Eggs lacking cuticle on the shell took up more water than those having cuticle. There was no correlation between water uptake and the water vapour conductance of cuticle‐less eggshells. 3. In general there was no correlation between the amount of water taken up by an egg and the weight of cuticle on its shell. With some eggs there was an association between water uptake and the extent of fissuring of the cuticle. 4. It is postulated that the pore canals impede water flow such that osmotic forces acting across the shell membranes do not influence water uptake by eggs.

Herbicide effects on the population growth of some green algae and cyanobacteria

Abstract: Six herbicides were tested for their effects on the population growth of a range of green algae and cyanobacteria by an easily replicated low-volume liquid culture technique using Repli-dishes. Diuron, propanil and atrazine were most inhibitory, chlorpropham was intermediate and MCPA and glyphosate were least inhibitory. Chlorpropham was more inhibitory to green algae than to cyanobacteria. The effects of chlorpropham and 3-chloroaniline, a metabolite, on populations of the cyanobacterium Anacystis nidulans and the alga Chlamydomonas reinhardii were monitored in larger scale batch cultures. Both compounds reduced the growth rate although in some cases there was partial recovery. 3-Chloroaniline was less inhibitory than the parent herbicide chlorpropham.

The influence of incubation temperature and pH on the antimicrobial properties of hen egg albumen

Abstract: Tranter H.S. & Board, R.G. 1984. The influence of incubation temperature and pH on the antimicrobial properties of hen egg albumen. Journal of Applied Bacteriology56, 53–6. Gram positive bacteria, including lysozyme-resistant strains, and yeasts were killed in hen egg albumen with or without iron at 30 of 39.5.dGC. The albumen was more toxic at 39.5.dGC than at 30dC for Gram negative bacteria. With the exceptions of Pseudomonas fluorescens, Acinetobacter sp. and Proteus vulgaris, iron caused the growth of Gram negative bacteria or protected them from being killed in hen albumen at 39.5.dGC. At this temperature, however, maximal growth of and glucose utilization by Escherichia coli C20 only occurred in albumen supplemented with growth factors, trace metals, additional nitrogen and sufficient iron to quench ovotransferrin. The bactericidal properties of albumen could be negated by changing its pH from 90 or above to 7.5 or below. At 39.5dC, enterochelin allowed growth of E. coli in albumen at pH 7.9, but not at 9.4, whereas iron allowed growth at both pH values.

Ultrastructure of vascular colonization by fungal wilt pathogens. II. Invasion of resistant cultivars

Abstract: Transmission electron microscopy was used to study vascular colonization in a resistant cultivar of tomato infected with Fusarium oxysporum fsp lycopersici or Verticillium albo-atrum and of pea infected with Fusarium oxysporum fsp pisi In both host species the pathogens were restricted to the vascular tissue of the roots and lower stems Restriction was associated with, and possibly due to, the occlusion of vessels in tap roots and hypocotyls In tomato the principal occluding reaction was the formation of tyloses and this was normally associated with extensive accumulations of electron-opaque material in the vacuoles of both the xylem parenchyma cells and the tyloses themselves Tyloses were absent in pea but vessels were occluded by gels The formation of both tyloses and gels could be induced by wounding The ontogeny of tyloses and gels and the possible involvement of these structures in resistance to wilt disease is discussed

Physiology of Cell Aggregation: Flocculation by Saccharomyces cerevisiae As a Model System

Abstract: An understanding of aggregation in a population of living cells is considered to involve six basic concepts or unit processes. These are the molecular architecture of the cell surface, the mechanisms by which dispersed cells are repelled, the forces which cause dispersed cells to aggregate, the changes in cell-surface architecture which cause a switch to aggregation, the structure of aggregates, and the importance of aggregation in the life-style of living cells. These concepts are considered using flocculation by the yeast Saccharomyces cerevisiae as a model.

Homoclinic, heteroclinic, and periodic orbits for a class of indefinite Hamiltonian systems

Abstract: Si E est l'espace euclidien de produit interieur (1), on etudie les orbites d'une classe de systemes hamiltoniens dans E×E quand la fonctionnelle d'energie est donnee par: H(q,p)=1/2(Sp,p)+V(q), (q,p)∈E×E et la forme quadratique (Sp,p) est indefinie mais non degeneree

D.C. magnetic properties of metallic glasses after flash annealing

Abstract: In this study, flash annealing involves passing a well shaped d.c. current pulse of known duration, through a straight strip of metallic glass. The rapid temperature rise (∼ 5000 K s-1), the high final temperature ( \sim500-600\deg C), the short pulse duration (112 ms), and the rapid cooling at the end of the pulse (∼500 K s-1) combine to achieve a thermal cycle unobtainable in a conventional furnace treatment. This study shows that a lower value of coercive field, H c , can be achieved after flash annealing than is possible in a furnace treatment. The uniaxial anisotropy, K u , is also reduced by flash annealing. A discussion of the results is given in terms of stress relief, creep enhanced relaxation and the total degree of relaxation attainable. A novel method of heat treating metallic glass cores is outlined, as an extension of this work.

The Numerical Calculation of Cusps, Bifurcation Points and Isola Formation Points in Two Parameter Problems

Abstract: In this paper we discuss the numerical computation of solutions of the nonlinear, two parameter, problem (1.1) where x ∈ R n is a State variable, λ and α are parameters, and f is a smooth function. Many physical systems can be described by equations like (1.1), see for example, [l],[3],[l2] and [7],[17], where there are more than two parameters.

The yeasts of British fresh sausage and minced beef.

Abstract: Three hundred and eighty three yeasts isolated from samples of unsulphited or sulphited sausages and skinless sausages and minced beef were characterized in detail.Debaryomyces hansenii was the most commonly isolated yeast from most samples followed byCandida zeylanoides andPichia membranaefaciens. The presence of sulphite in sausages did not appear to affect the numbers and range of yeasts present but did affect their relative proportions. A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.

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