bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reduction of False Diffusion in the Simulation of Vortex Shedding
Authors: Carey C , Scanlon T J , Fraser S M
Published: February 2007

The computational analysis of two-dimensional laminar vortex shedding from a rectangular bluff body in a confined channel flow is presented. In this analysis it is shown how the use of the conventional first-order hybrid-upwind convective differencing scheme provides an excellent example of the effects of multi-dimensional false diffusion. These effects are reduced substantially with the introduction of a new scheme, SU CCA (skew upwind corner convection algorithm), for the modelling of convective transport, resulting in the promotion of continuous vortex shedding. The introduction of the SVCCA scheme indicates that a complex transient phenomenon such as vortex shedding can be analysed using a modified first-order convection algorithm. The results also demonstrate the SVCCA scheme's ability to represent convective transport more accurately and hence help minimize the effects of multi-dimensional false diffusion in the numerical solution of the Navier-Slokes equation applied to laminar flow.
‘Natural’ Coordinates for Analysis of the Practical Stirling Cycle
Authors: Organ A J
Published: February 2007

The appropriate choice of coordinate system so simplifies basic cycle analysis that computation of the ideal particle trajectory diagram reduces to a straightforward graphical process. Ideal pressure, Reynolds number Nre, friction factor Cf and heat-transfer parameters Nst and N2/3pr follow in function of location and crank angle via a few steps on the hand calculator. A thermodynamic design parameter is identified which has essentially the same numerical value for such diverse Stirling engines as Philips' MP1002CA, General Motors' GPU-3 and the turn-of-the-century Kyko hot-air engine.
The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—Piezoviscous Behaviour
Authors: Hooke C J
Published: February 2007

In many line contacts the operating conditions, such as load, entrainment velocity and contact radii, vary with time. Generally, the results from standard elastohydrodynamic lubrication theory, derived for constant conditions, can be used to obtain a quasi-steady prediction of film thickness that is sufficiently accurate for design purposes. An important exception to this is where the entrainment direction changes because, under those conditions, the quasi-steady approach predicts that there will be no clearance between the surfaces while in practice a residual film will persist.

A previous paper showed that the minimum film thickness during entrainment reversal depends primarily on the rate of change of entrainment velocity. Limit expressions for the minimum clearance in the four regimes of lubrication were obtained. The present paper is part of a programme to develop a minimum film thickness chart for entrainment reversal and deals with the transition between the rigid-piezoviscous and the elastic-piezoviscous regimes.
Improved Positioning of Pneumatic Cylinder by Using Flexible Coupling between the Piston and Rod
Authors: Krejnin G V , Krivz I L , Smelov L A
Published: February 2007

Positioning accuracy of a pneumatic piston drive with flexible coupling between the piston and rod is considered. Improved positioning was expected due to the fact that the rod friction is usually considerably less than the piston friction. When the piston stops under the action of its friction force the rod continues the motion, providing the precision positioning of the output link. A mathematical model of a positioning pneumatic piston drive with two degrees of freedom was generated. Computer simulation of the performance of short and long strokes showed the feasibility of the improved positioning which provided design and control parameter optimization.
On the Non-Linear Characteristics of Automotive Shock Absorbers
Authors: Surace C , Worden K , Tomlinson G R
Published: February 2007

The objectives of this paper are essentially twofold. In the first case an experimental study of a number of shock absorbers is presented; the restoring force surface method of non-linear system identification is applied in order to determine the non-linear characteristics of the absorbers in an easily visualizable manner. In the second part, a new physical model for the absorber is presented which incorporates effects due to compressibility of the fluid in the absorber; this provides a more realistic representation of the stiffness characteristics than previous simple models. The new model is compared with the experimental data.
Optimization of the Tractive Performance of Articulated Tracked Vehicles Using an Advanced Computer Simulation Model
Authors: Wong J Y
Published: February 2007

This paper describes the results of a study of the effects of articulation joint configuration, suspension characteristics, location of the centre of gravity and initial track tension on the mobility of a two-unit, articulated tracked vehicle. The study was carried out using a comprehensive computer simulation model known as NTVPM-86. The results show that suspension characteristics, location of the centre of gravity and initial track tension have noticeable effects on the mobility of articulated tracked vehicles over marginal terrain, while the articulation joint angle has a less significant influence on vehicle performance. Locking the articulation joint between the two units of an articulated tracked vehicle usually causes a degradation of tractive performance. The approach to the optimization of the design of articulated tracked vehicles is demonstrated. It is shown that the simulation model NTVPM-86 can play a significant role in the optimization of articulated tracked vehicle design or in the evaluation of vehicle candidates for a given mission and environment.
Strategies to Meet US 1994/95 Diesel Engine Federal Emission Legislation for HSDI diesel Engine Powered Vehicles
Authors: Bürgler L , Herzog P L , Zelenka P
Published: February 2007

The forthcoming US passenger car and light-duty truck emission limits are currently the most stringent ones worldwide. The paper discusses which type of diesel engine has the best chance of fulfilling those requirements and what development strategy has to be followed.

A comparative analysis between IDI and DI diesel engines shows the potential of the HSDI diesel engine to meet NOx/particulates limits of 0.4/0.08 g/min while maintaining its fuel economy advantage.

Appropriate technological strategies are outlined. Besides the well-known technologies such as central position of injector and piston bowl, multi-valve cylinder head, inlet port swirl control etc., main emphasis is placed on the optimization of mixture preparation using fuel systems with variable injection rates as well as oxidation and DENOX catalysts.
The variation of in-Cylinder Mixture Ratios during Engine Cranking at Low Ambient Temperatures
Authors: Shayler P J , Isaacs R M , Ma T H
Published: February 2007

The development of mixture conditions in the cylinder of a fuel-injected spark ignition engine during engine cranking has been investigated at ambient temperatures down to —20°C. Mixtures near to the spark plug location were sampled and analysed to determine the air-fuel ratio and the relative proportions of light, medium and heavy components in the fuel. At low temperatures, the local air-fuel ratio varies substantially during the compression stroke, as does mixture composition. The change in mixture ratio over successive cycles of cranking depends on the fuel injected per cycle and the fuel-transfer characteristics of the intake port. The success or failure of combustion initiation is observed to depend only on the mixture air-fuel ratio at the spark plug. The upper limit on this mixture ratio for successful first-fire appears to be near to 35 : 1 by mass. Air-borne fuel in the cylinder accounts for only a small percentage of that supplied by the injector.
Measurement of Sound Insulation of Automotive Body Components Using Sound Intensity
Authors: Ling M K
Published: February 2007

A small-scale test facility is described which enables manufacturers to assess the sound insulation of noise reduction treatments. Designed to provide a cheap and quick alternative to standard test methods, the technique uses sound intensity to measure the insertion loss of noise reduction treatments when subjected to airborne noise.
The Rubber Road Friendly Suspension
Authors: Ashton B
Published: February 2007

The interaction between the vehicle suspension and the road has a significant effect on the road wear and damage. To address this problem an EC proposal has been issued to define a ‘road friendly suspension’. GKN Tadchurch have designed and tested a rubber tandem axle suspension that meets these EC proposals without compromising suspension articulation and roll stiffness.
Vehicle Electrical Power Supply Systems and Their Impact on System Design
Authors: Williams G A , Holt M J
Published: February 2007

The electrical power system is the vital lifeline to most of the control systems on modern automobiles. The following general trends are observed.

(a) increased use of electrically actuated systems, (b) increased use of electronic control, (c) increasing requirements for high-integrity power supplies for safety critical systems, (d) increased average electrical power consumption (heating, actuation, control systems), (e) increased electrical demand at engine idle combined with reducing idling speeds, (f) increased interest in higher voltage systems, (g) electrical system problems a major cause of roadside breakdowns.

These trends clearly indicate major changes in the requirements of vehicle electrical power supply systems and will demand considerable activity from the vehicle industry in the next decade. An important aim of this paper is to illustrate and promote a systems view of electrical power while considering existing and future problems and opportunities.
The Influence of Injection Rate Shaping on Diesel Fuel Sprays—An Experimental Study
Authors: Winklhofer E , Ahmadi-Befrui B , Wiesler B , Cresnoverh G
Published: February 2007

A current strategy in the development of direct injection (DI) diesel engine combustion systems is the control and limitation of the initial ‘premixed’ combustion heat release ensuing from the auto-ignition of the injected fuel. This requires control of the amount of fuel vaporization and mixing taking place during the ignition delay time. Since the latter is determined by the fuel composition and the in-cylinder gas temperature, development efforts have focused on the injection of well-controlled, portioned fuel quantities prior to the ignition as a means of achieving the desired goal. This practice is becoming known as ‘fuel rate shaping’. Consequently, the fuel spray penetration during this period, fuel evaporation and mixture preparation, as well as the influence of in-cylinder air motion on mixture distribution, are main subjects of interest in affording insight into fuel rate shaping attempts. These have been addressed through a combined experimental and theoretical investigation of the spray characteristics associated with different injection practices.

The experimental investigations have been performed in an optically accessed spray research engine. Basic aspects of fuel spray tip penetration, time and location of auto-ignition and flame propagation have been recorded with a high-speed line-scan camera. The results provide the space and time-scale characteristics for the propagation, ignition and combustion of a selection of diesel fuel sprays.

Investigations have been carried out for a conventional fuel injection system equipped with a set of different single-hole injector nozzles, as well as for a dual-spring injector and an injector with a split injection device. The experimental results provide an insight into the propagation of the fuel spray front, yield qualitative information about its spatial and temporal distribution, and, in the case of split injection, show the interaction of the initial pilot fuel portion with the main injection.
The Tribology of Engine Design
Authors: Neale M J
Published: February 2007

This paper reviews the technology of the tribological components of engines and presents a basic understanding of their design and operation. The availability of this basic understanding is put forward as an essential counterpart to computerized performance analysis programs for components with variable loads and speeds, such as crankshaft bearings, piston rings and cams and followers.
A Review of Internal Combustion Engine Losses Part 1: Specific Studies on the Motion of Pistons, Valves and Bearings
Authors: Ciulli E
Published: February 2007

Energy saving is an important task today. Friction reduction in reciprocating engines is a way to reduce fuel consumption and to improve engine endurance. To find the value of frictional losses of every component is necessary in order to reduce engine losses. The piston-liner system, valve train and bearings are the most important components for mechanical friction losses in reciprocating engines. In this paper both theoretical and experimental works published within the last ten years about the losses related to the motion of pistons, valves and bearings have been reviewed. Some known design improvements to reduce friction in these components are briefly reported and indications for future developments are pointed out, related in particular to the numerical approach, capable of more realistic simulations due to new software and hardware, and to the new experimental and material technologies.
Effects of Swirl on High-Speed Combustion in a Single-Shot Optical SI Engine
Authors: Han J O , Kim S S
Published: February 2007

Single-shot tests in a single-cylinder, optical SI engine operated by a rapid compression and expansion machine were performed in order to investigate the combined effects of engine speed, ignition position and swirl on early combustion and overall performance. For central ignition, swirl showed consistently favourable effects on combustion-related performance. However, at half-radius ignition the desirable swirl effect persisted at low engine speeds but faded away as the speed increased. This reversing of trends can be partially explained by differences in the maximum cylinder pressure, flame growth rate and flame front wrinkling.
Aerodynamics of Grand Prix Cars
Authors: Dominy R G
Published: February 2007

In recent years the remarkable performance of the Grand Prix car has been strongly influenced by aerodynamic design. Since the introduction of the current racing regulations the varied approaches to aerodynamic design have converged and to the casual observer current Formula ***I cars appear to be almost identical. This paper examines the aerodynamic considerations that have led to these designs.
A Model-Based Approach to the Automation of Failure Mode Effects Analysis for Design
Authors: Price C J , Hunt J E , Lee M H , Ormsby A R T
Published: February 2007

This paper describes the application of model-based technology in the area of failure mode effects analysis (FMEA). FMEA involves the repetitive application of engineering expertise, and so would seem to be a promising target for automation through knowledge-based systems (KBS) technology.

However, in order to decide what would be the effect of a failure in a sub-system, it is necessary to reason about the structure of the sub-system being investigated and to be able to represent and reason about different facets of the way in which the sub-system works. The difficulty of automating this analysis of failure effects for new designs has meant that, in general, automation of the FMEA task has concentrated on only the clerical aspects of FMEA—helping the human expert to keep track of which possible failures have been analysed.

The work described in this paper automates the analysis phase of the FMEA process. This should enable the development of computerized aids for the FMEA engineer which will eliminate much of the tediousness of the task.
Oil Pollution by the Offshore Industry Contrasted with Tankers: An Examination of the Facts
Authors: Sharples B P M
Published: February 2007

The topic of oil pollution of the sea by the offshore industry is topical in view of public reaction to the Exxon Valdez accident. The facts are examined to show whether the offshore industry's record is acceptable. Without such a rational examination and presentation of the facts and a global perspective, public pressure may lead governments, regulatory authorities and oil companies to act in such a way that the risk of oil pollution is increased. Oil-spills are examined on a global basis and several specific oil-spill cases are detailed. An outline of oil industry blow-outs shows that very little of the oil spilled into the oceans is derived from this source. Data on oil from drill cuttings and produced water is presented. The paper brings the various aspects together in a comparative analysis. Costs are also discussed. The conclusion is drawn that increasing the level of domestic exploratory drilling together with piping it to shore would in turn reduce the amount of imported oil in many countries. The reduced need for tankers would reduce the amount of oil spilled. Facts are also presented which show that both tankers and offshore drilling are less than 5 per cent of the source of oil in our oceans.
Systems Modelling and Control Applied to a Low-Pressure Gas Distribution Network
Authors: Parkinson J S , Wynne R J
Published: February 2007

A control system has been designed and implemented to provide more effective energy management of low-pressure gas distribution networks. The key to this is the provision of a control scheme that maintains low pressures across a network.

The work was approached from first principles and a modelling technique has been developed which provides reduced order models that adequately describe the characteristics of multi-feed gas networks. The models were then used for the control system design, which in this case also included the selection of the optimal measurement points for most effective control.

Following extensive design studies a relatively straightforward control scheme resulted which has been implemented and proved to be effective.
COmputer-Integrated Process Engineering—A Design Tool for Bioreactors
Authors: Weale D J , Walton D
Published: February 2007

Computer-integrated design techniques have been applied to the design and analysis of stirred tank bioreactors, and in particular their agitation systems. Bespoke software has been written for problem specification and preliminary design, with particular attention paid to data presentation and the user interface. The data generated can be passed to a large range of existing analysis, database and graphics software to enable detail design of each component. The result is a powerful design aid that in particular reduces the need for user speciality. This concept can be applied to any process or product that currently employs unrelated software in its design.
The Role of Maintenance Management Deficiencies in Major Accident Causation
Authors: Smith E J , Harris M J
Published: February 2007

There appears to be an increasing awareness that organizational and managerial factors play a critical role in ensuring plant safety. A detailed study is presented of one branch of industrial management, viz. maintenance management. It has highlighted the nature of some of the links between managerial practices and the reliability of plant equipment and personnel.

The causes of several major accidents are analysed using a systems approach, with the aim of understanding how the maintenance function was involved. A key conclusion is that, prior to major accidents, there is often a lack of detailed safety objectives and long-term safety control. Without these it becomes very difficult to assess the adequacy or otherwise of other maintenance management elements such as maintenance strategy, resources or administrative structure.

In the absence of tight safety and reliability control and consequent corrective actions a mismatch can develop between the perceptions of management and the actual condition of the plant.
Coverage of Non-Metals in the ASME B31.3 Chemical Plant and Petroleum Refinery Piping Code
Authors: Short II W E
Published: February 2007

The chemical and petrochemical industries have decades of experience in specifying metallic piping lined with non-metals as a cost effective alternative to high-priced alloy materials of construction for piping in corrosive service. Early on, application of plastic piping was essentially limited to atmospheric chemical sewage service and to above-ground vents and drains. However, applications and usage of plastic piping continue to increase as engineers become more confident in specifying plastic materials and mechanical contractors gain experience with their installation. Non-metallic materials are being developed that are not only corrosion resistant but also have increasingly higher pressure and temperature capabilities. Plastic double-containment piping has experienced tremendous growth for handling hazards and toxic fluids. In the United States, recent dramatic growth of plastic double-containment piping applications has been, to a large extent, for compliance with the Environmental Protection Agency (EPA) regulations of the 1976 Resource Conservation and Recovery Act (RCRA). Related EPA regulatory efforts were accelerated in 1988 by more stringent amendments to this legislation. Industry in the United States must comply with these EPA regulations by December 1998.

Plastic piping and metallic piping lined with non-metals have been covered to some extent by the ASME B31.3 Chemical Plant and Petroleum Refinery Piping Code for several years. The distinctive requirements of non-metallic piping and piping lined with non-metals were incorporated into the 1980 edition as a separate Chapter VII, which is dedicated to this growing area of interest in piping.

This paper provides an overview of the present coverage of non-metallic piping lined with non-metals in the ASME B31.3 Chemical Plant and Petroleum Refinery Piping Code (1). Some topics that warrant further investigation are presented as well.
Management and Technical Procedures for the Assessment of Defects Detected During In-Service Inspection of Pressure Systems
Authors: Hopkins P
Published: February 2007

Defects in pressure systems are often detected during in-service inspection. The significance of these defects can be assessed using fitness-for-purpose methods. These methods are usually applied by specialists but it is the pressure system user's responsibility to ensure the assessments are fully completed and reported on.
Conditioning Monitoring of Ethylene Main Pipeline Pumps
Authors: Lloyd S A , Ansley-Watson P
Published: February 2007

The pumping of ethylene at supercritical conditions over long distances demands sophisticated pumping stations. One condition that must be avoided at all times anywhere in the line is the generation of temperature hot spots, as these can lead to thermal decomposition of the ethylene under pressure with potential catastrophic consequences.

Both submerged motor driven pumps (canned pumps) and more conventional machines with mechanical seals have been used in this application: opinions are sharply divided as to which is the optimum design. The authors contend that no single answer exists but in either application the ability to safely disperse any leakage and to accurately diagnose machine conditions to detect any potential hot spots is of paramount importance. A sophisticated health monitoring is required for the pumps with temperature sensors as well as vibration monitors: the rate of temperature rise is an important parameter in these applications. This condition-monitoring installation should be linked back to the central control station via a SCADA (supervisory control and data acquisition) link.

Innovative condition-monitoring features such as temperature-measuring devices installed between each pump stage are reviewed and their potential benefits assessed.
The Mk 4 and Mk 5 Coaches for British Rail InterCity Part 1: The Mk 4 Coach SpecifiCation and Procurement
Authors: Higton J A , Temple D R
Published: February 2007

The story of the Mk 4 and Mk 5 coach developments from 1984 to 1991 is told by two members of the BR Project Team specially assembled to manage the procurement and entry into service of the new coaches. The paper is in two parts.

Part 1 of the paper opens with a brief résumé of BR coach development from the Mk 1 in 1951 through to the Mk 3 of the early 1970s. The Mk 4 coach was specifically designed for the electrified East Coast Main Line and formed part of a push-pull train called InterCity 225. The coaches were purchased under a new set of competitive procurement rules and as such the project team had to learn to deal with some new problems along with a lot of old ones.

Engineering developments were instigated in the areas of ride quality, braking and gangways and these are described. Interior mock-ups were also used to specify InterCity's requirements. The paper reviews preparation of the procurement specification, as well as the process of tendering and placing the contract. The design features of the Mk 4 coach are described, together with a brief description of the production and assembly process.
The Mk 4 and Mk 5 Coaches for British Rail InterCity Part 2: Testing, Commissioning and Service Experience with the Mk 4 Coach and Development of the Mk 5 Specification
Authors: Higton J A , Temple D R
Published: February 2007

The story of the Mk 4 and Mk 5 coach developments from 1984 to 1991 is told by two members of the BR Project Team specially assembled to manage the procurement and entry into service of the new coaches. The paper is in two parts.

Part 2 describes the testing, commissioning and service experience with the Mk 4 up to March 1991. Extensive ride development testing was necessary in order to enable the Mk 4 to meet its demanding ride specificiation. For the first time in nearly 20 years the ORE Climatic Testing Chamber in Vienna was used to test the complete coach at the specified extremes of temperature. Commissioning and service experience is discussed with details of some of the problems encountered and their solutions. The development of the Mk 5 coach engineering specification concludes the paper.
Parametric Study of a Railway Air Brake System
Authors: Murtaza M A , Garg S B L
Published: February 2007

This paper deals with the parametric study of a twin-pipe graduated release railway air brake system. The air brake model is based on the analysis of a pneumatic train circuit and a vehicle pneumatic circuit. The parametric study includes the effect of variation of the pneumatic train circuit and vehicle pneumatic circuit parameters. This shows that the computer simulation can be used to predict the performance while varying the design parameters during a brake application. The information is of vital importance for train operation and for laying maintenance and manufacturing tolerances of air brake system design parameters.
Brake Discs for Passenger Trains—a Theoretical and Experimental Comparison of Temperatures and Stresses in Solid and Ventilated Discs
Authors: Fermér M
Published: February 2007

The ventilated brake discs currently used in passenger trains can be replaced with solid discs when drag braking of long duration need not be designed for. This is a conclusion arrived at in the present study where transient temperatures and stresses induced in the disc during drag braking and during single and repeated stop braking are calculated by use of a previously established analytical model. The results are verified through full-scale experiments carried out on a recently built inertia dynamometer. A forged solid steel disc is compared with a standard ventilated cast iron disc. Measurement techniques and various observations are discussed.
Recent Developments in Light Rail Systems
Authors: Ware D K , Jones R N H
Published: February 2007

The 1980s saw a resurgence of interest in light rail systems throughout the world and particularly in Great Britain, where they had almost disappeared. Properly planned and executed they can effectively cater for a significant segment of city transport, using nonproprietary technology which is non-polluting and which can make use of a variety of energy sources.

This paper outlines some recent trends in the technology of light rail vehicles and control systems, and goes on to describe four new systems of different characteristics or stage of development.
Hong Kong Metro's Traction Equipment: The Drive for Efficiency
Authors: Moyes A D
Published: February 2007

This paper describes the evolution of the electric multiple unit traction equipment of the Hong Kong Mass Transit Railway Corporation (MTRC). Traction energy efficiency is particularly important to the MTRC and has been improved by 46 per cent on the most recently supplied cars. The justification for the conversion of the existing camshaft cars to chopper control and the relative merits of different types of drives in MTRC's application are discussed.

The utilization of energy, the method used to optimize coasting for energy saving, life-cycle costs and the design features of the gate turn-off thyristor chopper cars are described.
Brakes along the Line
Authors: Leigh M J
Published: February 2007

The Railway Division Chairman reviews his career in railway braking with Davies and Metcalfe, including his apprenticeship in the automobile industry.

He outlines his involvement with various multiple units in the United Kingdom and Australia, discussing the brake blending with its possibilities. The outcome of locomotive brake competition in the direct release market is described and the advantages of two-pipe brake systems for both direct and graduable braking are highlighted.

He concludes by mentioning training and the engineering profession.
Acceptable Noise Levels for New Railways
Authors: Shield B M , Roberts J P
Published: February 2007

There is, at present, no UK legislation controlling the noise that may be emitted by railways. The widespread concern over noise likely to be radiated from the Channel Tunnel Rail Link has highlighted this deficiency and in March 1990 the Government established the Mitchell Committee to recommend guidelines for a national noise insulation standard for new railways.

The results of previous studies of railway noise annoyance and the acceptability criteria that have been derived are examined with reference to recent research, and more effective criteria for social acceptability are suggested where new rail lines are concerned.
Track and Ground Vibrations from Trains Running on Conventional Ballasted Track
Authors: Ford R A J
Published: February 2007

This theoretical analysis predicts how spectra of track and ground vibrations from passing trains depend upon axle spacings in vehicles and sleeper spacings in track. At any measuring point on the surface of the ground, vibrations caused by trains running on conventional ballasted track are the combined effect of vibration waves propagating from every sleeper. The character of these vibrations is initially determined by the character of the vibration input that the train applies to each sleeper, but this is substantially modified by what happens as the resulting vibration waves propagate to the measuring point and superpose there. Propagation and superposition strongly modulate the input spectrum from trains, emphasizing vibrations at some frequencies in the measured response while minimizing vibrations at others. The shape of the final predicted spectrum depends upon the interrelationship of sleeper spacing and axle spacings, so it may be possible through careful choice of these dimensions to reduce the unwanted effects of train-induced vibrations—for example by minimizing excitation at known resonant frequencies of sensitive line-side structures. The predictions of the theory now await checking by experiment.
Development of Active Control Technology for the Next Generation of Combat Aircraft
Authors: Lee R N
Published: February 2007

In the mid 1970s British Aerospace recognized that active control technology offered considerable benefits in terms of improved performance and combat effectiveness for future combat aircraft. However, the introduction of such technology carried with it a significant development risk. In order to minimize that risk, a series of flight demonstrator programmes were initiated. This paper describes the principles of active control and the very successful fly-by-wire Jaguar and experimental aircraft demonstrator flight test programmes which progressively demonstrated the viability and benefits of active controls to the extent that this technology is being fully utilized on the new European fighter aircraft.
A Study of the Efficiency of a Double-Action Worm Gear Set
Authors: Burgess S C
Published: February 2007

A double-action worm gear set—so called because the worm has both rotational and longitudinal degrees of freedom—has been invented primarily for use in a motorized spacecraft hinge. This paper presents an analysis of the mechanical efficiency of the double-action worm gear set, together with preliminary test results. Results of analysis and test show that the double-action feature of the worm makes it possible to control the forward and backward driving efficiency of the gear set. Compared to a standard worm gear set, the double-action worm gear set has the advantages of the ability to absorb small applied displacements to the wormwheel shaft in an unlocked position, the ability to be non-backdrivable with a high degree of certainty when locked against an end stop and the ability to maintain a specific preload in a locked position.
The Suppression of Single-Fin Buffeting Using Tangential Leading Edge Blowing on a Delta Wing
Authors: Bean D E , Wood N J , Mabey D G
Published: February 2007

The application of tangential leading edge blowing to reduce levels of single-fin buffeting has been studied. The tests were performed at the University of Bath in the 2.1 m × 1.5 m wind tunnel using two cropped 60° delta wings. To measure the buffet excitation, a rigid fin instrumented with miniature differential pressure transducers was used. A flexible fin of similar planform and size was used to measure the buffeting response. Steady state static pressure data and laser light sheet flow visualization were employed to aid interpretation of the vortical flow over the wings, and hence identify the causes of the buffeting. The profiles of the buffet excitation and response were found to match each other very closely.

It was observed that the leading edge blowing modified the leading edge vortices by reducing the ‘effective angle of attack’ of the vortex. Blowing at a constant rate shifted the buffet excitation and response to higher angles of attack. Flow visualization confirmed that the mechanism at peak buffeting had not changed, but had been merely shifted. It has been shown that the use of an optimum blowing programme could completely suppress the buffeting response.
Development of a Large Deployable Space Reflector Structure
Authors: Russell A G
Published: February 2007

This paper describes the selection, configuration, design and development of the 5 m diameter deployable reflector structure currently being undertaken jointly by British Aerospace Space Systems Limited and the University of Surrey.

Large reflectors represent the most likely, near-term application of a large deployable space structure and offer the most promising opportunity for the development and qualification of the hardware required. Such a large, deployable reflector has to compete against other reflector designs which are not suitable for development into larger space structures but are optimized solely as reflector backing structures. These competitors provide a useful measurement of performance against which the development reflector may be compared in terms of mass, stiffness, cost and reliability.

The proposed reflector comprises a radio frequency reflective surface of gold-plated molybdenum knitted wire mesh supported from the nodes of a tetrahedral truss. The development 5 m diameter reflector is made from six deployable tetrahedrons configured symmetrically around a central node. Larger reflectors are possible using the same concept with longer struts or by using an extension of this concept with extra rings of tetrahedrons. The solution is dependent upon the required reflector size and stowage volume restrictions.

This design has brought together two critical items of hardware for a large deployable space structure: a simple, light, reliable self-latching hinge (developed by the Ministry of Defence and the University of Surrey) and a long, light, stiff, inexpensive carbon fibre tube (manufactured by the pultrusion technique).
Aeronautical Engineering Education for the Armed Forces
Authors: Duggins R K
Published: February 2007

A discussion is given of the arrangements that have been made for aeronautical and aerospace engineering education of members of the armed forces in the United Kingdom, the United States of America, West Germany and Australia. A striking feature of the comparisons is shown to be the extent of the differences in the arrangements in the various countries. A less detailed and less rigorous version of the paper was presented at the Aerotech 92 conference (1).
A Model of the Geometrical Changes in Aortic Valve Leaflets in Response to Leaflet Extension and Variable Boundary Conditions
Authors: Fisher J , Butterfield M , Lockie K J , Davies G A
Published: February 2007

The function, deformation and performance of heart valve leaflets are dependent on the material properties and the geometry of the leaflet. As the leaflet acts as a constrained membrane the geometry is dependent on the boundary condition applied to the leaflet and any permanent extension of the leaflet. Both of these factors are varied during the preparation of frame-mounted porcine bioprosthetic heart valves and surgical insertion of free-sewn valves. This can result in abnormal geometry and function. A mathematical model has been developed which describes these changes in geometry of a cylindrical leaflet as a function of the diameter of the aortic root (boundary conditions) and the length (or permanent extension) of the leaflet. Both the angle of inclination and the radius of curvature of the cylindrical leaflet were reduced with increased leaflet length or decreased aortic diameter. Agreement was found between the model predictions and experimental observations in porcine bioprosthetic heart valves, where abnormal leaflet geometries are produced by non-physiological boundary conditions and permanent set of the leaflets by fixation with glutaraldehyde. The general solutions developed in this model allow leaflet geometries to be predicted for a range of conditions in free-sewn and frame-mounted valves.
Reconstruction of the Anterior Cruciate Ligament
Authors: Seedhom B B
Published: February 2007

Ligaments are strong collagenous structures that act as constraints on joint motion, thus confining the articular surfaces to more or less the same paths. In so doing they prevent arbitrary apposition of these surfaces from occurring and resulting in abnormal stresses which may damage the joint surfaces. Ligaments rupture due to excessive loads, particularly those resulting from trauma occurring during sporting events or motor vehicle accidents. Knee and ankle joints have the highest frequency of ligamentous injuries.

This paper is a brief review of the current approaches to the reconstruction of the knee ligaments with specific reference to the anterior cruciate ligament (ACL) being the most frequently reconstructed. This is not only because it is frequently injured but also because of the debilitating consequences of such an injury. Approaches ranging from the conservative to those that advocate the use of frank prosthetic replacement have been adopted by surgeons at both ends of the spectrum.

Following a discussion of the rationale for reconstruction of the ACL, the mechanical and biological considerations of the reconstructive procedure are discussed. The different methods of ACL reconstruction are reviewed. These include: (a) primary repair, (b) reconstruction with different tissues, including autogenous allografts and xenografts, (c) reconstruction employing different synthetic devices.

A brief discussion of the procedures used for reconstruction with different types of tissue and of the surviving examples of the synthetic devices will follow.
A Comparison of Various Loading Configurations of the Proximal Femur for the Evaluation of Reconstructive Surgical Procedures
Authors: Schmotzer H , Tchejeyan G , Song J
Published: February 2007

The study was designed to evaluate the effect of different loading configurations on stem and bone stresses in simulated total hip arthroplasty. The traditional experiment design of loading the model through the head of the prosthesis by the resultant joint force was compared with a more realistic model which included an abductor strap to simulate the abductor muscle force. In addition, an alternative experiment design was evaluated in which a loading arm was clamped directly on to the head of the prosthesis. The results show that loading the model by the resultant joint force not only changes the magnitude of the stresses but also the stress distribution compared to the abductor muscle model. The new experiment design closely approximates stresses seen in the abductor muscle model below the lesser trochanter. In the proximal region, the stresses are increased on the medial side and decreased on the lateral side. The advantages of the proposed loading model are: (a) easy and reproducible set-up and alignment is facilitated, (b) different positions of the femur (flexion, extension) can be simulated and (c) a more realistic stress distribution and magnitude is achieved.
The Measurement of Blood Flow Waveforms from X-Ray Angiography: Part 1: Principles of the Method and Preliminary Validation
Authors: Brunt J N H , Wicks D A G , Hawkes D J , Seifalian A M , du Boulay G H , Colchester A F C , Wallis A
Published: February 2007

The principles and implementation of a method for measurement of blood flow waveforms from X-ray angiography are described. Contrast medium mass values are obtained at multitudinous positions along individual vessels and from numerous images in a time sequence. These values are represented as a matrix of grey levels in a parametric image. This image is normalized to represent contrast medium concentration, and the movement over time of isoconcentration portions of the contrast bolus is recovered to determine blood flow. Preliminary validation has been undertaken using parametric images generated in two ways: synthesis from a computer model of vascular pulsatile flow and analysis of cine-angiograms of physical models (plastic and perspex tubes) carrying known pulsatile flows. Two distinct methods for interrogation of parametric images by digital image processing were employed; both provided accurate flow measurements.
The Measurement of Blood Flow Waveforms from X-Ray Angiography: Part 2: Application to Video Recordings of Digital Subtraction Angiography
Authors: Brunt J N H , du Boulay G H , Wallis A
Published: February 2007

A method of measuring blood flow from X-ray angiograms recorded on cine film, by obtaining contrast mass values at numerous positions along individual vessels and at multiple instants of time, has been previously reported. In the present work it was hypothesized that the signal-to-noise limitations of recordings on video tape could be overcome by recording already-subtracted angiograms from a digital subtraction angiographic (DSA) system and that the spatial resolution of video was adequate to use a similar measurement method. Validation experiments were recorded, in which flows measured using a calibrated electromagnetic flowmeter passed through tubes of 4–7 mm diameter, during injections of 2–5 ml contrast medium. The video sequences were computer analysed and produced angiographic flow measurements agreeing with the electromagnetic flows to within 5 per cent. A case study of a clinical carotid artery DSA in a patient with secondary carcinoma metastases in the brain is described. It is concluded that accurate flow measurements can be made from DSA video recordings.
Determination of the Arterial Flow Fraction in Normal and Diseased Livers Using Constrained Deconvolution
Authors: Barber D C , Tindale W B
Published: February 2007

There is some evidence that the ratio of the blood flow to the liver through the hepatic artery to the total flow to the liver through the hepatic artery and portal vein (the hepatic arterial flow fraction, AFF) is altered in the presence of cirrhosis. Several methods have been published that seek to provide an index of this ratio. These indices are dependent on factors other than the AFF and cannot provide a true measure of it. The impulse retention function of the liver has two components and these may be derived using a model-driven deconvolution of the arterial tracer concentration curve and the curve of tracer concentration in the liver. The AFF may then be obtained from the relative heights of these two components. Simulation studies show that the AFF calculated using this method is reasonably accurate and a small clinical series shows that it is capable of appropriate clinical classification of patients into cirrhotic and non-cirrhotic groups.
The Effect of Porosity of Articular Cartilage on the Lubrication of a Normal Human Hip Joint
Authors: Jin Z M , Dowson D , Fisher J
Published: February 2007

The effect of porosity of articular cartilage on the lubrication of a normal human hip joint has been studied. The poroelasticity equation of articular cartilage and the modified Reynolds equation for the synovial fluid lubricant have been successfully solved under squeezefilm motion and for the conditions experienced in a normal human hip joint. It has been shown that porosity of the articular cartilage depletes the lubricant film thickness, rather than increasing it, particularly when the lubricant film thickness becomes small. Furthermore, it has been shown that articular cartilage can be treated as a single-phase incompressible elastic material in the lubrication modelling under physiological walking conditions.
The Transmission of Translational Seat Vibration to the Head: The Effect of Measurement Position at the Head
Authors: Paddan G S , Griffin M J
Published: February 2007

Head motion has been measured in six axes on twelve subjects exposed to vertical seat vibration in the frequency range 0.5–25 Hz. The subjects sat on a rigid flat seat in two postures: ‘back-off’ (no backrest) and ‘back-on’ (subject's back in contact with the seat backrest). Translational acceleration has been calculated for various locations on the head and transmissibilities between vertical seat vibration and translational head motion determined for each location and all axes. The translational motion of the head was most affected by pitch motion of the head. This caused variations in fore-and-aft motion with position along the vertical axis of the head and variations in vertical motion with position along the fore-and-aft axis of the head. These variations are illustrated for each subject in both postures. The individual data allow the identification of various modes of vibration and show that seat-to-head transmissibility is greatly affected by pitch modes of the head and neck. The magnitude of motion occurring in some modes is dependent on body posture.