Showing papers by "Cranfield University published in 1983"

Improved data correlations for buoyancy-driven convection in rooms:

Abstract: Improved data correlations have been derived for buoyancy-driven convective heat transfer from the internal surfaces of naturally-ventilated buildings. They cover the full range of laminar, transitional and turbulent airflows, and are based on the mathematical model of Churchill & Usagi (1972). The new correlating equations are presented in a convenient form for incorporating into modern computer programs which simulate the dynamic thermal performance of buildings. They compare favourably with the available exerimental data for isolated surfaces, and are shown to be an improvement on the ‘standard’ correlations recommended in the CIBS Guide. The factors which affect the accuracy of such data correlations, when used for the energy-conscious design of ‘real’ buildings, are briefly discussed.

Driving after stroke

Abstract: SummaryStroke patients were compared with “normal” drivers. On public roads stroke patients exhibited special difficulty in entering and leaving motorways and handling traffic at roundabouts. On private roads stroke patients were relatively unaware of other vehicles, exhibited difficulty in reversing, had difficulty in doing two things at once in an emergency and had difficulty in placing their car accurately on the left. Analysis revealed variables that might be used to rate stroke patients on their driving skills.ResumeLe comportement de sujets hemiplegiques conduisant une voiture adaptee fut compare a celui de conducteurs en bonne sante. Dans la circulation routiere, les hemiplegiques eprouvent plus de difficulte en s'engageant et en quittant les autoroutes et au passage de grands carrefours. Sur un chemin prive, le sujet hemiplegique ne tient que peu compte de la presence d'autres vehicules; il lui est relativement difficile d'effectuer correctement une manoeuvre en marche arriere, de combiner deux ge...

Addition of polyethersulphone to epoxy resins

Abstract: Phase separation of polyethersulphone from solution in epoxy resins has been studied as a function of polyethersulphone concentration, type of resin, and curing conditions. The resins chosen were a rapidly curing tetrafunctional and a trifunctional epoxy resin, hardened with either diaminodiphenylsulphone, or dicyandiamide. Fracture surfaces of some of the cured blends exhibited nodular features between 0.2μm and 6μm in diameter. Using X-ray microanalysis and scanning electron microscopy these nodules were shown to contain high concentrations of polyethersulphone. Mechanical properties, including fracture energy, dynamic mechanical relaxation and creep, were studied for the same range of blend compositions. Dynamic mechanical spectra provided further evidence for phase separation in certain blends, while elastic modulus, fracture toughness and creep showed little dependence upon composition.

Multivariate Analysis of the Relationship between Drivometer Variables and Drivers' Accident, Sex, and Exposure Status

Abstract: Drivers classified by sex, accident history, and driving exposure drove a 50-km route in an instrumented car. Run time, speed changes, fine and coarse steering-wheel reversals, accelerator and brake applications, lateral accelerations, gear changes, traffic-free speed, signals, and overtaking were recorded. Aggression and anxiety tests were also administered, and discriminant analyses were performed on the results. In general, the personality variables did not discriminate between driver groupings. With regard to driving variables, however, significant and important discriminations between groups were made. Accident-involved drivers drove more quickly on clear roads, moved about more, and overtook in traffic. When moderate-exposure drivers were examined, both female and male accident-free drivers were typified by relatively low mean clear speed, infrequent overtaking, and frequently being overtaken. In addition, accident-free females used the brakes relatively infrequently. Accident-free males did not move the car about in traffic. Overall, high-exposure male drivers tended to drive relatively quickly, but those who were accident free were typified by adjusting their car to changing conditions (brake applications, gear changes, accelerator applications, and possibly coarse steering-wheel reversals).

Applications of electron transfer between biological systems and electrodes.

Abstract: The demonstration of rapid and reversible electron transfer between cytochrome c and a gold electrode in the presence of 4,4’-bipyridyl (Eddowes & Hill, 1977; Albery et al., 1981) offered the opportunity for development of a new generation of bioelectrochemical devices. Extension of this work on ‘promoted‘ electron transfer to other redox proteins such as bacterial ferredoxin (Armstrong et al., 1982), together with successes in coupling oxidoreductases such as nitrate reductase to these modified electrodes (Hill et al., 1981), provided a means of tightly linking enzyme-catalysed reactions to solid electrodes. A complementary method of achieving direct electron transfer is the use of chemical ‘mediators’, which, unlike the ‘promoters’ they replace, undergo redox reactions during translocation of electrons between proteins and electrodes (Plotkin et al., 1981; Turner et al., 1982a,b). Mediators may also be immobilized on or within the electrode surface, which when coated with an appropriate oxidoreductase provide commercially important catalytic electrodes.

Second order theory of unsteady burner-anchored flames with arbitrary Lewis Number

Abstract: Three theoretical models of plane flames burning on a cooled porous-plug type of flame-holder are reviewed and compared with experimentally observed relationships between stand-off distance, flame speed and temperature. It is shown that for most practical burners their conductance is large and that for near adiabatic conditions, the order of the non-dimensional stand-off distance ceases to be O (1), but is O (O) where O is the non-dimensional activation energy. Starting in 1946 as the College of Aeronautics, the Cranfield Institute of Technology was granted university status in 1969. In 1993 it changed its name to Cranfield University.

Close-following on the motorway

Abstract: In an observational study of over 2000 close-following (tailgating) incidents in the centre lane on the Bedfordshire stretch of the Ml motorway, 20% involved a gap of less than 0·5 s. The proportion of lorry tailgaters was about equal to that of car tailgaters, although a disproportionately greater number of lorries were involved in ‘rear-end shunt’ collisions, as recorded by Bedfordshire County Council. Leading/tailgating vehicle dyads were significantly more frequently lorry/lorry and car/car than they were either lorry/car or car/lorry. When the state of other lanes, during tailgating, was examined, it was found that outside-lane-being-clear (unnecessary) but inside-lane-being-clear (provoked) tailgating by cars was greater than expected by chance, while simple unnecessary car tailgating was less. Provoked lorry tailgating, however, was less than expected, although greater when the inside lane was occupied (unprovoked), regardless of the state of the prohibited outside lane. When lane state and dyad co...

Prediction of interfacial filler thickness for minimum thermal contact resistance

Abstract: Presentation et verification experimentale d'une procedure theorique d'optimisation de l'epaisseur d'un materiau d'insertion pour minimiser la resistance thermique de contact entre des surfaces planes rugueuses

Mathematical Modelling of Heat and Mass Transfer in Agricultural Grain Drying

Abstract: Mathematical modelling and computer simulation of grain drying are now widely used in agricultural engineering research. Several models have been proposed to describe the heat and mass transfer processes involved in the drying of agricultural products. Most of these models, however, have been derived under assumptions that are not explicitly stated and that restrict their applications from the outset. Furthermore, it is not always clear what differences, if any, exist between various models. The purpose of this paper is to provide a general framework from which mathematical models for any type of drier may be derived. We illustrate the use of this framework by deducing equations for the four basic types of convective grain drier, namely fixed bed, crossflow, concurrent flow and counterflow. Finally we discuss some of the differences between the models thus obtained and those of other workers.

Unstable capillary flow of reinforced polymer melts

Abstract: The injection capillary flow of various unfilled and glass fibre or calcium carbonate filled polypropylene and nylon 6.6 melts is studied using either a single capillary of five capillaries in series, separated by small reservoirs. Only unfilled nylon 6.6 yields instability during flow through a single capillary due to mechanochemical degradation in the capillary at extremely high shear rates above 5 × 105 s−1. It is found that only short glass fibre reinforced polypropylene yields high frequency oscillations in the reservoir pressure and extrudate diameter and has discontinuity in the flow curve when the apparent shear rate is above 4 × 105 s−1 and the flow is through multiple capillaries. Further increase in the shear rate restores the stable flow. The intensity of the oscillations and the range of shear rate during which unstable flow occurs are increased with increasing melt temperature. The mechanism of this unstable flow is investigated by studying fibre orientation at the capillary entrance and exit using mouldings simulating capillary entry-exit flows.

The ultimate load sensitivity of lipped channel columns to column axis imperfection

Abstract: An analytical investigation is made of the effect of column axis imperfection on the equilibrium behaviour and ultimate carrying capacity of thin-walled lipped channel columns. The Rayleigh-Ritz method is used to obtain local buckling loads and a semi-energy method is employed to describe post-buckling interaction behaviour. In the analysis a facility of allowing the locally deflected form to change after buckling is provided, resulting in asymptotic equilibrium curves tending towards continually changing reduced Euler loads as opposed to fixed reduced Euler loads based on an unchanging locally deflected form. The imperfection sensitivity of column designs which produce stable and unstable equilibrium behaviour after local buckling is investigated as is that of columns which exhibit neutral equilibrium behaviour before local buckling. Results are presented in the form of non-dimensional load-deflection equilibrium curves and ultimate load-slenderness plots covering these three equilibrium states. A comparison of the theory with independent experimental work is also included.

Managing Manufacturing Operations in the U.K.

Abstract: This paper describes some of the major findings relating to the management of manufacturing operations which have emerged from survey work originally carried out in conjunction with the British Institute of Management. More detailed follow-up studies are also outlined relating to delivery performance and a particular industrial sector: capital electronics goods. The paper summarises the main results of the original survey based on replies from manufacturing managers in 186 plants (representing 158 companies), relating to the characteristics of the companies surveyed, the personal and career details of the responding managers, the nature of the manufacturing operations carried out in the 186 plants, particularly with regard to customer delivery performance and manufacturing lead times, use of computers and sophisticated techniques in manufacturing, and the control systems used in the initiation of production orders. Finally, calling on data from later studies, an attempt is made to focus attention on the key issues in manufacturing management as they relate to U.K. industrial performance.

Co-injection molding of reinforced polymers

Abstract: Co-injection molding of calcium carbonate filled polypropylene, short glass-fiber-filled polypropylene, or unfilled high-density polythylene melts is studied using a mediumsize injection-molding machine and a center-gated disc mold. Injection molding is carried out under non-isothermal conditions. Order of injection of the melts, injection speed, and mold temperature is changed in order to understand the mold filling in general and to investigate the type of skin/core structure and mechanical interlocking of the phases in the moldings. It is found that the order of injection is not significant in obtaining a skin/core structure but it is important in obtaining extensive phase interlocking, which is reduced if the flow rafe and the mold temperature are low. Presence of fillers appears to result in more mechanical interlocking of the phases.

Simulation of Centrifugal Compressor Transient Performance for Process Plant Applications

Abstract: The development of a theoretical model capable of simulating centrifugal compressor transient performance (including compressor surge) is detailed. Simulation results from a Fortran computer program are compared with measured compressor transient data. Good simulation of compressor transients between stable operating points, and compressor presurge flow oscillations has been obtained. General application criteria are presented for the geometric distribution of model elements within a compressor system. Model applications and future work are outlined.

Precision engineering aspects of record player design

Abstract: Delegates at the First International Precision Engineering Seminar, held at Cranfield in May 1981, heard one of the first public demonstrations of the Elite-Cranfield gramophone. This design was developed at Cranfield as an attempt to obtain the maximum information from the analogue (black vinyl) record, while adding the minimum of additional signal (distortion). This article describes the basic requirements of a high quality gramophone record player, focussing on some of the precision engineering techniques which were applied in the Cranfield design, and illustrating how the application of advanced technology may be necessary, even in domestic ‘consumer’ products, where the highest level of performance is an important criterion of success.

Simulation of centrifugal compressor transient performance for process plant applications

Abstract: The development of a theoretical model capable of simulating centrifugal compressor transient performance (including compressor surge) is detailed. Simulation results from a Fortran computer program are compared with measured compressor transient data. Good simulation of compressor transients between stable operating points, and compressor presurge flow oscillations has been obtained. General application criteria are presented for the geometric distribution of model elements within a compressor system. Model applications and future work are outlined.

Anisotropic etching of silicon. a model diffusion-controlled reaction

Abstract: In conventional isotropic etching of metals, it has been found that narrower slots take longer to etch than wider ones. This has been attributed largely to the restricted access of fresh etchant to the metal surface. Spent etchant remains at the metal surface and forms a physical etch-retarding barrier. Anisotropic etching of single crystals differs from isotropic etching, in that it is orientation dependent, and different crystal planes are etching at different rates under identical conditions. This investigation examines anisotropic etching of (110) silicon for different slot widths and compares it with the already available information on isotropic etching of metals [1].