Showing papers by "City University London published in 1985"

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Abstract: Analyse et discussion du texte publie par Bradford ― reproduit en annexe ― en 1934 et contenant le premier enonce de sa fameuse loi. Les difficultes rencontrees a l'epoque par Bradford sont analysees a la lumiere des etudes faites depuis lors. (INTD)

The Free Rider Problem and a Social Custom Model of Trade Union Membership

Abstract: The literature on public good provision by groups has traditionally emphasized the free rider problem. If it is assumed that a group forms to provide, or to lobby for the provision of, a good that is collective to potential members, then the major conceptual problem to the formation of such a group is that individuals can enjoy the benefits of group action without incurring the costs. By doing this, they free ride. In small groups the free rider problem is not generally considered insurmountable. However, the larger the number of potential beneficiaries, the more difficult it is to overcome the free rider problem, due to exclusion and surveillance difficulties, and the less likely is optimal collective good provision, or any collective good provision in the extreme. The free rider hypothesis has a long history in economic thought. As early as 1848, the free rider potential of any group of workers was perceived by J. S. Mill. However, it appears that it was not until 1965 that an attempt was made to explain why large groups providing collective goods manage to exist despite the free rider problem. Olson [1965] proposed the following explanation. If a large group exists, it must have formed either because membership is compulsory or because the group provides private goods and services accessible only to its members, with ancillary provision of the collective good as a "byproduct." The literature that developed from Olson's work has focused primarily on the suboptimal provision of the collective good, the difficulties of getting members to contribute in proportion to the benefits received, and preference revelation incentives. (See for example Groves and Ledyard [1977].) However, there are problems with both of the solutions proposed by Olson to overcome the free rider problem facing large groups. First, if coercion is looked at as a solution to the free rider problem, the question arises as to how the coercion itself is financed [Guttman, 1978]. This is unlikely to be costless. The second problem concerns the "byproduct" solution. Private good pro-

Mathematical model of the human renal system.

Abstract: A mathematical model is presented which provides an overall description of the renal/body fluid system, comprising an interconnected set of physiologically based representations of the relevant subsystems of the human organism. The model is used to test a number of hypotheses relating to the dynamics and control of the human renal system, including dynamics of ADH clearance, glomerular tubular balance and the control of the rate of release of ADH. Results are presented establishing the validity of the model in a number of empirical tests.

Oxygen Evolution on Nickel Oxide Electrodes

Abstract: Etudes du degagement anodique d'oxygene sur NiO lie au Teflon et sur NiO dope avec Li, dans une solution de KOH, par methodes potentiostatique et galvanostatique en fonction de la concentration d'ions OH − . Deduction de l'equation cinetique

The dissolution of iron from the negative material in pocket plate nickel-cadmium batteries

Abstract: A common mode of failure of nickel-cadmium flooded pocket plate cells is iron poisoning of the positive plate due to transfer of iron into the active material from active materials and materials of construction Nickel plated steel pockets are sometimes used to minimize iron dissolution, particularly on the positive electrode Sometimesα-Fe2O3 is used as an additive to the cadmium electrode This paper assesses the extent of dissolution of iron fromα-Fe2O3 by using electron microscopy, X-ray crystallography, cyclic voltammetry, coulometric and atomic absorption measurements

Joint coordination method for the steady-state control of large-scale systems

Abstract: The advantages of several methods for the steady-state control of large-scale systems are combined to give an algorithm which produces optimum solutions for a wide class of processes. It is demonstrated how optimum reality solutions can be obtained even when large model-reality differences exist. The method employs a hierarchical framework where coordination of local decision problems is achieved jointly by price and modifier variables. A three-subsystem process is optimized to illustrate the procedure.

Industrial classification in UK capital markets: a test of economic homogeneity

Abstract: This paper reports the results of a test of the ability of the Stock Exchange industrial Classification system (SEIC) to provide homogeneous industry groupings of firms. Aggregation into ‘meta-industries’ is also explored. The analysis shows that while there are significant differences between the 14 SEIC industries considered, several appear to be largely nonhomogeneous with respect to certain of their fundamental economic and structural characteristics. Given this lack of homogeneity it is arguable that the SEIC has fallen shorts of its stated objectives with potential implications for the allocation of resources in UK capital markerts. The greater homogeneity of the four meta-industries derived indicate that use of industry groups at a higher level of aggregation than the SEIC might be more appropriate. A subsidiary objective of the investigation was to examine the potential benefits from adopting a quadratic discriminant methodology as opposed to the more conventional linear rule for studies of a rela...

A System of Models for Fluid-Electrolyte Dynamics

Abstract: In this paper, a number of models which have been developed for studying fluid-electrolyte equilibrium and imbalance is presented. Two levels of dynamics and control are considered corresponding to the physiological processes and the incorporation of such processes within the clinical dynamics of patient care. The large-scale simulations presented are used mainly for hypothesis testing or giving insight into the complex physiological dynamics, whereas the clinical models, which are smaller, are used for parameter estimation and predicting the evolving patient state. Computer simulation is central to these model developments in generating time responses for model identification, validation, and prediction. The paper examines the possible clinical application of the various models in the management of fluid-electrolyte disorders and indicates that features of each of them, integrated into a single implementation, could provide a system of practical clinical value.

Migration during early married life.

Abstract: A one per cent sample drawn from the 1971 Census (the OPCS Longitudinal Study) was used to study the migration patterns of women in the early years of first marriage. Information from the retrospective fertility and migration history contained in the 1971 Census record was analyzed and the results show migration at, or soon after, marriage to be almost universal. Marriage migrants constituted a quarter of all one-year within-county movers and a fifth of inter-regional movers among women aged 16–29. In the early years of marriage differentials in migration rates according to duration of marriage were greater than differentials associated with age or with husband's change of occupation. The pattern of migration around marriage varied according to a number of socio-economic factors. The timing of the first and subsequent births early in marriage was found to have little effect on migration rates once allowance for duration of marriage was made in the analysis. The results of the study demonstrate the value of the OPCS Longitudinal Study as a source of migration data.

The stability of flows in channels with small wall curvature

Abstract: The ‘stability’ of flows in symmetric curved-walled channels is investigated by essentially combining Fraenkel's ‘small’ wall-curvature theory with the multiple-scaling (or WKB) method. The basic flow is characterized by the steady-state stream function Ω, which varies ‘slowly’ in the streamwise direction. An asymptotic scheme is posed for Ω in such a way that at lowest order Ω represents a class of Jeffery–Hamel solutions. An infinitesimal disturbance is superimposed on the basic flow through a time-dependent stream function Φ, and the resulting linearized disturbance equation suggests that fixed-frequency disturbances with ‘slowly’ varying wavenumber are appropriate. The asymptotic scheme for Φ yields the Orr–Sommerfeld equation at lowest order. Two classes of channels are considered. In the first class the curvature is constant in sign, and under certain conditions they reduce to symmetric divergent straight-walled channels. In the second class of channels the curvature varies in sign, and these may be more suitable for experimentation. A spatially dependent growth rate of the disturbance relative to the basic flow is defined; this forms the basis of the ‘stability’ analysis. Critical Reynolds numbers are deduced, below which the disturbance decays as it travels downstream, and above which the disturbance grows for a limited range in the streamwise direction. For the first class of channels the ‘stability’ analysis is carried out locally, and the dependence of the critical Reynolds numbers on curvature and higher-order terms is investigated. For the second class of channels the ‘stability’ analysis is carried out at various positions downstream, and an overall minimum critical Reynolds number is predicted for a range of channels and flows.

Mathematical modelling of industrial thermometers

Abstract: The dynamic response of temperature sensors is of importance to both the designer and user of sensors. Understanding the factors affecting the dynamic response of such sensors would be beneficial. The present paper reports on research conducted in the development and application of mathematical models to predict the dynamic behaviour of a complex thermometer assembly. It is shown that such models can be used to predict step fluid temperature responses and deliberate self-heating responses both to within a few per cent. Distributed-parameter and lumped-parameter models were developed and validated for a platinum resistance thermometer with and without a well. These relate thermometer performance to material properties and detailed geometry and hence to constructional features. Such models can be used for (a) thermometer design studies including sensitivity analysis to find the significant contributions to the thermometer dynamics and (b) in situ response testing from the electrical port using the deliberat...

An experimental investigation of the behaviour of thin-walled box beams

Abstract: The purpose of this paper is to present the results of an experimental investigation of the behaviour of four types of thin-walled box beam and to compare the results with those obtained from theoretical analyses. Three steel models consisting of a straight single cell cantilever, a curved single cell cantilever and a simply supported twin box have been constructed, in addition to a continous prestressed concrete two-span double cell beam. Details are given of the methods of construction, instrumentation and experimental procedure for all the models. The behaviour of the individual models has been studied, with particular attention being given to the torsion and distortion of the box sections, the cross-sectional distributions of the longitudinal and transverse bending stresses and the deflections. Appropriate experimental results are presented, therefore, and are compared with those obtained from the specially developed thin-walled box beam finite element which has been presented previously in this journal.

Perceptual factors affecting colour order systems

Abstract: The perceptual colour attributes relevant for ordering unrelated, related, luminous, and nonluminous colours are different insome respects. Colour order systems for related nonluminous colours have been the most fully developed, but different systems depend on different types of experimental data, such as equalization of small perceptual differences, colour scaling, and some relationships to properties of the stimuli. The resulting systems have both similarities and differences, which are worthy of careful study. Chromatic adaptation is an important factor affecting and appearances of samples of colour order systems viewed in illuminants of various colours, and requires further study.

Visual acuity screening for diabetic maculopathy

Abstract: We have investigated the use of visual acuity (VA) as a screening test for diabetic maculopathy in an outpatient setting. The best corrected VA was recorded under standardised conditions in 197 of 223 randomly selected patients ⩾ 50 years old. True VA was ⩽ 6/12 in one or both eyes of 69 patients (35%). Of 183 diabetic case notes examined, 51% had no VA previously recorded. In the remaining patients, results differed from last recorded VA in 46% of eyes. An ophthalmologist examined 110 patients without knowledge of VA and his findings were combined with details of recorded eye examinations of 50 patients already attending an eye clinic. Eighty-nine per cent of patients with subnormal acuity had “clinically discernible eye disease” compared with 23% of those with normal acuity. Twenty-two per cent of patients with subnormal acuity had diabetic maculopathy compared with 1% of those with normal acuity. A normal VA provides reasonable assurance that maculopathy is not present and, when expert fundoscopy for elderly patients is in short supply, specialist attention should be concentrated on patients with abnormal acuity.

Gas evolution on porous electrodes

Abstract: The factors governing the choice and strength of electrocatalyst aggregates in Teflon (PTFE) bonded electrodes are discussed in terms of their preparation routes. For electrocatalysts prepared via physical routes, the aggregates are very weak while those prepared via chemical routes are strong enough to withstand the pressures generated inside the pores during gas evolution reactions. Effectiveness factor and catalyst loading investigations show conclusively that the existence of dry PTFE channels provide a convenient pathway for the gas bubbles to escape, thereby ensuring the interior of the electrode will not be completely denuded of electrolyte, thus allowing more of the electrocatalyst surface to be utilized.

Effect of an organic additive on the impedance of cadmium in alkaline solution

Abstract: The a.c. impedance of a planar cadmium electrode in KOH solution was measured over the active and passive region using a potentiostatic technique. Different concentrations of polyvinyl alcohol (PVA) were subsequently introduced into the alkaline solution and the impedance remeasured. It was found that the addition of PVA markedly increased the double layer capacity of the electrode and decreased electrolyte resistance,R sol. The impedance spectra in the presence of PVA were analysed in terms of an equivalent circuit involving the series combination of two double layer capacitances and a resistance proportional to the conductivity of the electrolyte.