Showing papers by "Cranfield University published in 1972"

On the Inverse Relationship of Recall and Precision.

Abstract: It is now ten years since some slight experimental evidence was presented which appeared to support the hypothesis that there was an inverse relationship between recall and precision. The idea of this was certainly not new; Fairthorne had more than implied it in his discussions on OBNA and ABNO systems, i.e. Only‐But‐Not‐All (high precision) and All‐But‐Not‐Only (high recall). However, it was one of the propositions arising from Cranfield I which met with strong opposition and was quite rightly attacked. In reply to the critical review by Swanson, I had to agree that the simple hypothesis required modification. By the following year test results coming from the experiments by Salton and from Cranfield II made further modification necessary, and the hypothesis was finally put forward to read as follows: ‘Within a single system, assuming that a sequence of sub‐searches for a particular question is made in the logical order of expected decreasing precision, and the requirements are those stated in the question, there is an inverse relationship between recall and precision, if the results of a number of different searches are averaged. This, it will be noted, has four important qualifications to the basic statement.

Hydrogen generation by means of the aluminum/water reaction

Abstract: An aluminum amalgam will react with water at ordinary temperatures with the formation of aluminum hydroxide and the liberation of free hydrogen. In the case of a block or sheet of the metal having an amalgamated surface, this reaction will continue until all the aluminum has been consumed. The reaction rate is observed to be temperature dependent, and this affords a simple means of regulating the output of hydrogen. If the supply of water and disposal of waste is discounted the reaction is shown to be superior, on a volumetric basis, to all other common means of producing hydrogen, and furthermore is competitive on a weight and cost basis with other chemical production methods. The inherent simplicity of such a scheme for hydrogen generation offers attractive advantages in terms of reliability.

Effects of Fuel Injection Method on Gas Turbine Combustor Emissions

Abstract: A series of tests have been carried out using a single segment of a tuboannular, aircraft-type, gas turbine combustion chamber to investigate the influences of operating conditions and fuel injection method on exhaust emissions. The test range included pressures up to 200 psia and inlet air temperatures from 380 to 900°K (684 to 1620°R). Concentrations of nitric oxide, carbon monoxide, unburned hydrocarbons and smoke were determined from gas samples obtained in the combustor exit plane.

Prediction of inert turbulent swirl flows

Abstract: Numerical finite-difference predictions are made of inert turbulent boundary-layer swirling flows. A variety of turbulence models are considered and a nonisotropic model is found to show more realistically the effects of swirl on jet development. Gross effects may be represented by an extended Prandtl mixing length model but constants appearing do not exhibit universality. This deficit is partially overcome by the use of an algebraically-modeled, nonisotropic energy-length turbulence model. The Richardson number and the local swirl number play important parts in linking the rtf-shear with the rx-viscosity and the nonisotropy of the turbulent viscosity.

Measurement of the Mechanical Properties of Growing Surface Films in oxidising environments

Abstract: The mechanical properties of surface scales on iron and nickel have been previously measured, during growth at high temperatures, using a vibrational technique (1,2). The feasibility of using this technique to study other systems is discussed and, in particular, its application to high-temperature, oxidation rate and oxide stability on the results are considered and values of the Youngs modulus of the oxide scale on Nimonic 90 over a range of temperatures have been determined. Messung der mechanischen Eigenschaften von in oxydierender Umgebung entstehenden Oberflachenfilmen Die mechanischen Eigenschaften von Oberflachenzunder auf Eisen und Nickel wurden mit Hilfe einer Vibrationstechnik schon fruher bei hohen Temperaturen wahrend des Wachstums bestimmt. Die Moglichkeit der Anwendung dieser Methode zur Untersuchung anderer Systeme wird erortert und besonders die Anwendung auf Hochtemperaturlegierungen wird untersucht. Der Einflus von Temperatur, Oxidationsgeschwindigkeit und Oxidstabilitat auf die Ergebnisse werden erortert und der E-Modul des Oxidzunders auf Nimonic 90 wurde in einem groseren Temperaturberich bestimmt.

Trailer coupling means

Abstract: Arrangement for coupling a trailer drawgear to a towing road vehicle, in which a frame, arranged for pivotal connection with rear parts of the towing vehicle, carries at a rear part thereof a ball connector for receiving a socket connector secured on the trailer drawgear and below that ball connector a pair of steerable wheels, in which arrangement the wheels are steered by a lever pivoted on the frame and engaging in a steering device fixed on the trailer drawgear.

Improved formulation of Gummel's algorithm for solving the 2-dimensional current-flow equations in semiconductor devices

Abstract: By a transformation of variables, the equations of Gummel's algorithm achieve a form which avoids the recurrent calculation of exponentials that usually characterises the method. The transformation results in tractable equations and a reduction in computational labour compared with previous methods.

Planning the Distribution System: an operational approach

Abstract: This monograph considers recent developments in management techniques and proposes their use in physical distribution system planning. The recent developments in physical distribution management are reviewed and the author considers how such techniques as missions analysis and systems thinking may be combined into a useful planning model with which the problems of physical distribution system design may be analysed and solved. The monograph is not specific in that it does not offer management “ten easy steps to system design”. It takes a broad view of the problems involved and is concerned with an approach to system planning rather than specific problem solutions.

Measuring and counting systems

Abstract: A digital displacement sensing device for sensing the relative displacement of two parts of a mechanism comprises a linear scale having digital indicators, a reading head which can traverse along the scale and means for selectively adjusting the angle between the centre line of the scale the direction of relative displacement of said parts for adjusting the amount of said relative displacement which corresponds to the distance between two adjacent ones of said digital indicators.

Mass Transfer Technique for Investigation of Heat Transfer by Jet-Impingement Systems:

Abstract: The technique of using mass transfer measurements (by sublimation of naphthalene) together with the Chilton–Colburn analogy is shown to be feasible for evaluation of heat transfers from impinging jets. The method is then used to determine heat transfer coefficients at the burner walls in models of jet–impingement furnaces.

Heat Transfer and Flow in a Short, Vertical, Internally Heated Annulus with a Rotating Outer Boundary

Abstract: Experimental determinations were made of the steady-state heat fluxes and velocity profiles in water between two vertical concentric cylinders, the heated inner cylinder being stationary while the outer cylinder was rotated in ambient temperature air Secondary flows, due to end effects, existed in the annulus at all rotational speeds and profoundly influenced the rate of heat transfer across the annulus When the circulation of the secondary flows opposed those due to natural convection, the mean Nusselt number decreased almost to unity

Analysis and measurement of the relative movements between the road wheels of a vehicle and the road surface.

Abstract: A method of analysis of suspension performance has been developed and is supported by experimental evidence. The particular advantage of this analysis is that all the suspension characteristics of real suspensions are calculated for all possible positions of the suspensions in a manner which relates the wheel movements directly to the body motions. The roll centre concept is discarded, with the result that the wheel movements, and hence tyre forces, which were masked by the limitations of the roll centre assumptions, are now available for examination and inclusion in any vehicle study. This has resulted in the development of more realistic models of vehicle ride and handling including anti-dive attitudes and other phenomena.