Showing papers by "University of Exeter published in 1988"
TL;DR: The Statistical Tools for Simulation Practitioners (SSPP) as discussed by the authors is a set of tools for simulation practitioners that can be found in the Textbooks and Monographs Series, Vol. 76.
Abstract: 17. Statistical Tools for Simulation Practitioners (Statistics: Textbooks and Monographs Series, Vol. 76). By J. P. C. Kleijnen. ISBN 0 8247 73333 0. Dekker, New York, 1987. 448 pp. $83.50.
607 citations
TL;DR: The results throw doubt on the suggestion that the Late Closure strategy is favoured (in English) mainly because it is efficient in information processing terms and suggest that different languages make use of parsing strategies in an essentially arbitrary way.
441 citations
267 citations
TL;DR: This is the first detailed investigation on an insect performing the varied patterns of ‘natural’ flight of six butterfly species, and analyses and field observations suggest possible correlations between flight performance and wing shape.
Abstract: Representatives of six butterfly species, flying freely in the field or in simulated field conditions, were filmed with a high-speed cine camera and subjected to kinematic and morphometric analysis. This is the first detailed investigation on an insect performing the varied patterns of ‘natural’ flight. Kinematic parameters in representative sequences of selected flight modes were calculated and compared, and wing shapes were characterized using aspect ratio and non-dimensional moment parameters.
The analyses and field observations of these and other butterflies suggest possible correlations between flight performance and wing shape. The behaviour of individual species conforms reasonably well with crude predictions based on aspect ratio, wing loading and wing inertia.
254 citations
TL;DR: In this article, a model of an insect wing is described in which spars of corrugated membrane which incorporate stiffening veins branch serially from a V-section leading edge spar.
Abstract: A model insect wing is described in which spars of corrugated membrane which incorporate stiffening veins branch serially from a V-section leading edge spar The mechanical behaviour of this model is analysed
The open, corrugated spars possess great resistance to bending, but are compliant in torsion Torsion of the leading edge spar will result in torsion and relative movement of the rear spars As a result camber will automatically be set up in the wing as it twists
Aerodynamic forces produced during the wing strokes will result in torsion and camber of the wing which should improve its aerodynamic efficiency
The effects of varying parameters of the wing model are examined For given wing torsion, higher camber is given by spars branching from the leading edge at a lower angle, by spars which curve posteriorly, and by spars which diverge from each other
Wings of three species of flies were each subjected to two series of mechanical tests Application of a force behind the torsional axis caused the wings to twist and to develop camber Immobilizing basal regions of the leading edge greatly reduced compliance to torsion and camber, as predicted by the theoretical model Aerodynamic forces produced during a half-stroke are sufficient to produce observed values of torsion and camber, and to maintain changes in pitch caused by inertial effects at stroke reversal
237 citations
TL;DR: In this article, a new scattering matrix formalism for the modeling of electromagnetic wave propagation in stratified media is presented, which is computationally efficient and stable and is well suited to the layer geometry that is characteristic of stratified materials.
Abstract: We present a new scattering matrix formalism for the modeling of electromagnetic wave propagation in stratified media. It is computationally efficient and stable and is well suited to the layer geometry that is characteristic of stratified materials. It is applied successfully to the modeling of total attenuated reflection in nematic liquid crystals with beyond-critical-angle incidence when the conventional transfer matrix methods normally fail.
207 citations
195 citations
TL;DR: Soil biological processes can be considered a hierarchy of successive levels of organization where the macro-, meso- and microfauna influence microbial activities at different scales in the habitat mosaic.
Abstract: The processes of C and N mineralization carried out by microorganisms are affected directly and indirectly by invertebrates over a wide range of spatial and temporal scales. Microfauna track temporal changes in bacterial and fungal populations in soil microsites, particularly in the rhizosphere, which alters the dynamic balance between N mobilization and immobilization. The feeding activities of mesofauna can determined the distribution, activities and composition of fungal communities. Macrofauna have major effects on fungal and bacterial activities, both directly, through feeding and gut passage, and indirectly, by affecting the microbial environment in litter and soil. Soil biological processes can therefore be considered a hierarchy of successive levels of organization where the macro-, meso- and microfauna influence microbial activities at different scales in the habitat mosaic. The spatial components of this hierarchy are integrated by plant roots; root morphology must therefore define the scales at which the system operates under different plant nutrient regimes.
179 citations
TL;DR: Analysis of the movement of individual regions of the wing shows further that inertial effects will produce the tip to base ‘torsion wave’ seen inthe wing at stroke reversal, and a simplified inertial model is developed to calculate the angular velocity about the torsional axis that would be caused by wing inertia.
Abstract: The cause of the changes in wing pitch at stroke reversal in Diptera has been investigated. The high compliance of the wing base makes it seem unlikely that pitch changes are caused by active torsion at the wing articulation. The centre of mass of insect wings tends to be behind the centre of torsion of the wing, and it is proposed that wing inertia about the torsional axis alone is responsible for pitch changes as the wing is accelerated at stroke reversal. A simplified inertial model is developed to calculate the angular velocity about the torsional axis that would be caused by wing inertia. The mass distribution and the torsional axis of the wings of two species of flies was found and it was shown that in these animals inertial causesalone could develop the angular velocity in the pitching plane that is observed at stroke reversal. Analysis of the movement of individual regions of the wing shows further that inertial effects will produce the tip to base ‘torsion wave’ seen inthe wing at stroke reversal.
167 citations
TL;DR: In this article, an examination of suspended sediment storage within a 35 km stretch of the main channel of the River Exe, Devon, UK, has been undertaken and some results are presented in this paper.
Abstract: Summary An examination of suspended sediment storage within a 35 km stretch of the main channel of the River Exe, Devon, UK, has been undertaken and some results are presented in this paper. Methodological problems associated with a field investigation of this nature are outlined and a technique for measuring suspended sediment storage in gravel-bed rivers is documented. The findings of the study indicate that for the River Exe, channel storage of suspended sediment is minimal and equivalent to less than two per cent of the annual sediment yield. In this river the main channel acts primarily as an efficient conveyance system through which sediment is rapidly transported from the basin.
156 citations
TL;DR: The importance of sediment-associated transport in the movement of contaminants through terrestrial and aquatic ecosystems has been highlighted by a growing interest in the physical and chemical properties of fine grained-sediment, both in terms of the role of erosion processes in controlling the properties of sediment at source and the transport of particulates through river systems as discussed by the authors.
TL;DR: A cluster analysis showed that Pinus tissues can be separated from Fagus tissues on the basis of their endophyte populations, and a K-means cluster analysis revealed that eleven of the fungi isolated were mainly responsible for this separation.
Abstract: Fifty-three endophytes were isolated from whole stem and xylem tissues taken from a mixed stand of Pinus sylvestris and Fagus sylvatica. Rhinocladiella atrovirens appeared confined to the xylem of Fagus, Coniothyrium cf, pini to the xylem of Pinus. Coryneum betulinum, Cryptocline sp. 1 and 2, Cylindrocarpon album and Melanconium atrum occurred in whole stems of Fagus only, Coniochaeta tetraspora and Sporormiella australis in whole stems of Pinus. Five species were non-host specific and occurred in all four morphological units. A cluster analysis showed that Pinus tissues can be separated from Fagus tissues on the basis of their endophyte populations, and a K-means cluster analysis revealed that eleven of the fungi isolated were mainly responsible for this separation. A discriminant analysis performed with these fungi demonstrated good discrimination between the four tissue sample groups.
TL;DR: The feeding and burrowing activities of macrofauna, notably termites and earthworms, also modify the physical properties of soil and litter habitats with important consequences for water balances of soils, water infiltration rates, overland flow and sediment transport.
TL;DR: In this paper, the vertex numbers of pentagon+hexagon polyhedra of icosahedral, tetrahedral or dihedral symmetries were analyzed and the existence of closed electronic shells was shown.
Abstract: General formulas are presented for the vertex numbers, ν, of pentagon+hexagon polyhedra of icosahedral, tetrahedral or dihedral symmetries. Criteria for uniqueness of representation, isomer counts and grouping of pentagons are established. All polyhedra with 256 vertices or less and belonging to T, D5, D6or their supergroups are listed. With the addition of C3ν to the dihedral and higher groups, at least one pentagon+hexagon cluster is found for all even ν≥20 except for ν = 22 which is unrealisable in any symmetry, and ν = 46 (for which a C3 polyhedron exists). Carbon clusters with closed electronic shells are shown to be generated by a geometrical leapfrog procedure: for all ν = 60+6k (where k is zero or greater than one) at least one closed shell structure is predicted. In dihedral symmetry closed shells also exist for some other values of ν. Separation of the 12 pentagonal faces is not sufficient to ensure a closed electronic shell but appears to be a necessary condition in dihedral or tetrahedral symmetry.
TL;DR: In this article, a predictive model for estimating the density and distribution of Badger social groups, in the south-west of England, based on habitat characteristics, was described, and a preliminary study to define the different types of badger sett observed in the field and to establish a relationship between main sett density and social group density was conducted.
Abstract: This paper describes a predictive model for estimating the density and distribution of Badger social groups, in the south-west of England, based on habitat characteristics. Main sett density was used as an index of Badger social group density, and a preliminary study to define the different types of Badger sett observed in the field and to establish a relationship between main sett density and social group density is also described. The habitat characteristics that emerged as having the most influence on Badger social group density were the ‘diggability’ of the soils, the topography of the area, altitude, the length of hedgerows and the number of woodland units greater than 1 ha. The application of the model is briefly discussed.
TL;DR: In this article, the authors studied stream nitrate levels in a small catchment of mixed land use (the Slapton Wood catchment) have been studied since September 1970; a record of this length is possibly unique in the United Kingdom for such a small basin (94 ha).
Abstract: Stream nitrate levels in a small catchment of mixed land use (the Slapton Wood catchment) have been studied since September 1970; a record of this length is possibly unique in the United Kingdom for such a small basin (94 ha). A sustained increase in nitrate concentration has been observed during the study period. In addition to this long-term trend, short-term changes in nitrate concentrations relate to stream discharge levels and to seasonal variations. Multivariate statistical analysis has been used to quantify these trends and to identify those factors controlling the production and loss of nitrate from the catchment system. The main period of nitrate removal occurs in winter when high concentrations coincide with the main period of throughflow generation. The influence of climatic variability is illustrated by reference to the 1975/76 drought and post-drought period.
TL;DR: In studies of the lysis of rabbit erythrocytes, red beet cells, andPenicillium notatum protoplasts by the potato glycoalkaloids α-solanine and α-chaconine, the latter was consistently the more membrane-disruptive compound and ery Throcytes the more susceptible cell type, and synergistic effects in all three test systems were pronounced.
Abstract: In studies of the lysis of rabbit erythrocytes, red beet cells, andPenicillium notatum protoplasts by the potato glycoalkaloids α-solanine and α-chaconine, the latter was consistently the more membrane-disruptive compound and erythrocytes the more susceptible cell type. A 1∶1 mixture of solanine and chaconine produced pronounced synergistic effects in all three test systems. In beet cells, such effects were apparent from an early stage of treatment and persisted over a period of several hours. With erythrocytes and fungal protoplasts, the synergism was maximal with mixtures containing approximately 70% chaconine, whereas with beet cells it peaked at approximately 40% chaconine. Synergistic interactions between solanine and chaconine also occurred with regard to cholesterol binding in vitro, with a maximum response corresponding to the 50% mixture. The implications of these findings for the nature and efficacy of chemical defense systems in plants are discussed.
TL;DR: An experiment is described in which newborn infants were habituated to a square-wave grating oriented 45° from vertical, and significant preferences for the novel, mirror-image, grating were found, a result which argues for some degree of visual cortical functioning at birth.
Abstract: There is some controversy concerning whether or not the visual abilities of the newborn are mediated entirely through subcortical pathways or whether the visual cortex is functioning at birth. A critical test of cortical functioning is discrimination of orientation: orientation-selective neurons are found in the visual cortex but not in subcortical parts of the visual system. An experiment is described in which newborn infants were habituated to a square-wave grating oriented 45 degrees from vertical. After habituation, significant preferences for the novel, mirror-image, grating were found, a result which argues for some degree of visual cortical functioning at birth.
TL;DR: In this paper, the authors show that the level of intelligence is reliably related to observable physiological variables, variability in basic mental processing mechanisms, the capacity to learn or remember, fundamental thinking skills, the ability to reason abstractly, complexity of a person's cognitive functioning, adaptability or mental flexibility, executive controlling functions, or unspecified biological mechanisms, or that indications of measured intelligence level precisely identify intellectual qualities that an individual possesses.
Abstract: Although the level of someone's intelligence is frequently put forward as being a possible reason for that person's success or failure at intellectual tasks, intelligence level is in reality only a descriptive measure, not an explanatory concept. Ten conceivable states of affairs are described, which if proved to contribute to or be indicated by measured intelligence would legitimize the assertion that a statement about someone's intelligence can help to explain their degree of success at mental tasks. These are that level of intelligence is reliably related to (1) observable physiological variables, (2) variability in basic mental processing mechanisms, (3) the capacity to learn or remember, (4) fundamental thinking skills, (5) the ability to reason abstractly, (6) the complexity of a person's cognitive functioning, (7) adaptability or mental flexibility, (8) executive controlling functions, or (9) unspecified biological mechanisms, or (10) that indications of measured intelligence level precisely identify intellectual qualities that an individual possesses. The evidence fails to provide firm confirmation of the existence of any of these 10 states of affairs, indicating that measures of intelligence level have little or no explanatory value.
TL;DR: A questionnaire was used to investigate gambling in British adolescents as mentioned in this paper, and responses from fifty 13- to 14-year-olds were analyzed, finding that 90% of the subjects reported at least some gambling activity.
Abstract: A questionnaire was used to investigate gambling in British adolescents. Responses from fifty 13- to 14-year-olds were analyzed. Gambling was found to be very pervasive (90% of subjects reported at least some gambling activity). Males gambled more than females, both in absolute terms and as a proportion of income. Income was found to have some influence on gambling behavior, but the effects of intelligence and social class were nonsignificant. Slot machines were the commonest form of gambling in both sexes.
TL;DR: The radiation of aquatic Diptera, from the Jurassic onwards, was immensely important, revolutionising the structure of many ecosystems and resulting in the colonisation of several new adaptive zones.
TL;DR: In this paper, the hydrogen-bond lengths for axially symmetric dimers were determined on a consistent basis for the series B…HF and B…HCl, where B=N2, CO, PH3, HCN, CH3CN, NH3, or (CH3)3N and X=F, Cl or CN.
TL;DR: The central point of Horace's epistle to the Pisones (ll. 220-50 out of 476) is a lengthy passage on the history and composition of satyr-plays as discussed by the authors.
Abstract: At the central point of Horace's epistle to the Pisones (ll. 220–50 out of 476) is a lengthy passage on the history and composition of satyr-plays. At the central point within that passage (ll. 234–5), with emphatic use of the vocative and the first-person pronoun, Horace presents himself and his addressees as actively involved in writing satyr-plays:non ego inornata et dominantia nomina solumverbaque, Pisones, satyrorum scriptor amabo.
TL;DR: In this paper, it is shown that a viscous fluid flow with curved streamlines can support both Tollmien-Schlichting and Taylor-Gortler instabilities.
Abstract: It is known that a viscous fluid flow with curved streamlines can support both Tollmien-Schlichting and Taylor-Gortler instabilities. The question of which linear mode is dominant at finite values of the Reynolds numbers was discussed by Gibson & Cooke ( Q. Jl Mech. appl. Math . 27, 149 (1974)). In a situation where both modes are possible on the basis of linear theory a nonlinear theory must be used, however, to determine the effect of the interaction of the instabilities. The details of this interaction are of practical importance because of its possible catastrophic effects on mechanisms used for laminar flow control. Here this interaction is studied in the context of fully developed flows in curved channels. Apart from technical differences associated with boundary-layer growth the structures of the instabilities in this flow can be very similar to those in the practically more important external boundary-layer situation. The interaction is shown to have two distinct phases depending on the size of the input disturbances. At very low amplitudes two oblique Tollmien–Schlichting waves interact with a Gortler vortex in such a manner that the scaled amplitudes become infinite at a finite time. This type of interaction is described by ordinary differential amplitude equations with quadratic nonlinearities. A stronger type of interaction occurs at larger input disturbance amplitudes and leads to a more complicated type of evolution equation. The solution of these equations now depends critically on the orientation of the wavefronts of the Tollmien–Schlichting waves to the Gortler vortex. Thus, if the angle between the directions of the vortex and the waves is greater than 41.6° this stronger interaction again terminates in a singularity at a finite time; otherwise the breakdown is exponential, taking an infinite time. Moreover, the stronger interaction can take place in the absence of curvature, in which case the longitudinal vortex is entirely driven by the Tollmien–Schlichting waves.
TL;DR: In this paper, the authors report the results of a test of two hypotheses on the similarity of information needs of different users of financial reports in Nigeria among themselves and with the needs of similar users in some developed countries.
Abstract: Implicit in the publication of general-purpose external financial statements by domestic and multinational enterprises and in the increasing interest in international accounting harmonization and standardization is the belief that the information needs of users are similar on the national and international scenes. A number of research studies have investigated the existence (or non-existence) of a consensus on the needs of different users within a nation and cross-nationally but no study has been reported on the needs of users of financial reports in developing countries. There is, however, much a priori discussion of the apparent differences between the needs of users in this group of countries and those of users in the western industrialized countries. This paper reports the result of a test of two hypotheses on the similarity of information needs of different users of financial reports in Nigeria among themselves and with the needs of similar users in some developed countries.
TL;DR: In this paper, the results of an experimental study of a totally symmetric prism/silver film/air gap/ silver film/prism system are presented in which both symmetric and antisymmetric surface plasmon-polaritons (SPP) are optically excited using 632·8 nm radiation.
Abstract: Results of an experimental study of a totally symmetric prism/silver film/air gap/silver film/prism system are presented in which both symmetric and antisymmetric surface plasmon-polaritons (SPP) are optically excited using 632·8 nm radiation. Data taken over a range of air gap thicknesses illustrate many interesting features in accordance with predictions made using Fresnel's equations. The manner in which the two coupled SPPs evolve in terms of Poynting vector distribution and electric field profiles within the structure is studied in detail. Both the transmitted and the reflected attenuated total reflection signals are investigated.
TL;DR: In this paper, the authors analyse the theoretical development and assess the extent to which understandings and explanations of classroom processes and outcomes have been enhanced, and where future developments might lie.
TL;DR: In this paper, the authors examined tax policies designed to correct the attendant externalities in the presence of asymmetric information and screening costs, and showed that when projects differ in expected returns it is ambiguous whether costly private screening weakens or strengthens the case for an interest income tax.
TL;DR: In this article, the Gibbons and Laughton equation of state was used to model the phase diagrams of pure fluids and the implications of this equation for the representation of pure fluid, and of binary and ternary mixtures are discussed.