bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation of Thermal Insulation of IDI Diesel Engine Swirl Chambers
Authors: Charlton S J , Campbell N A F , Shephard W J J , Cook G , Watts M J
Published: February 2007

The paper describes a computational and experimental study of the application of advanced ceramic materials for thermal insulation of the swirl chamber of the passenger car IDI diesel engine. Four ceramic materials, having a wide range of physical properties, were evaluated. These were syalon 101, aluminium titanate, reaction bonded silicon nitride (RBSN) and tetragonal zirconia polycrystals (TZP). A detailed finite element study was carried out in support of component design which examined parameters such as heat flux, operating temperature, thermal and assembly stresses and evaluated the requirements for interference fits between metallic and ceramic components. Experimental work was initially carried out on a steady state dynamometer test stand and later supported by vehicle tests on a chassis dynamometer and test track.

The investigation has shown that current engineering ceramic materials have the potential for application in engine combustion chambers. A total of 254 hours of engine testing with ceramic chambers was achieved without catastrophic engine failure. Engine performance was unchanged by the adoption of a thermally insulated swirl chamber, probably because the increase in swirl chamber surface temperature obtained (increased from 660 to about 850°C at full load) was insufficient to modify the thermodynamic cycle. Hydrocarbon emissions were generally increased, however; this was due in part to the difficulty of sealing the air gap behind the ceramic chamber at the fuel injector and glow plug interfaces.
Process Safety—An Engineering Achievement
Authors: Kletz T A
Published: February 2007

Up to the late 1960s the chemical industry looked upon safety as a non-technical subject but after a number of serious accidents technical people with production experience began to be appointed as safety advisers. There had been so little systematic thinking that it was not difficult for them to make improvements such as:

the development of systematic methods, now widely used, for identifying and assessing hazards, the development of inherently safer designs (in contrast, the industry has been slower to adopt this change), the development of a new attitude towards human error.

These, and other, changes produced a dramatic improvement in the industry's accident rate and raised the reputation of the subject to today's level.

The 1980s were a period of consolidation rather than innovation. Finally, we look ahead to the 1990s.
An Analytical Approach to the Effects of Production Tolerances in Product Evaluation and Routine Quality Control
Authors: Lawrence C C
Published: February 2007

Quality control procedures check either for dimensional accuracy or for particular performance characteristics of a product, but rarely for an integration of both. Dimensional accuracy is almost exclusively concerned with tolerance allowance, but functional characteristics are concerned with the nominal performance or state values. The consequence of such an approach is that the tolerance is not linked directly with the functional performance and, as such, is likely to convey the impression, if large variations are observed, that they are due to some intrinsic deviation in the product's performance or that there is an inconsistency within the material that is at fault.

This paper uses the production of plastic fuel and water pipe to illustrate the cumulative effects that quite sensible and economic tolerance allowances may have upon performance data.
A Computational Modelling Approach to the Design of Stable Ventilation Systems
Authors: Boucher R F , Kissane M P
Published: February 2007

The well-known glove box arrangement used in the nuclear industry maintains a pressure depression within a contaminated volume while allowing passage of a small purge flow to the filtration plant. Conventionally, if a glove tears for example, an electromechanical control system restores the depression by opening and regulating an extra connection to the filtration duct. However, faster response and lower maintenance overheads result from replacing the conventional system with the fluidic vortex amplifier (VA) but coupled ventilation system and VA dynamics can be unstable. Designers needed a tool to predict oscillatory performance and, ideally, to advise on the strengths of influence of network parameters on stability.

A system modelling approach is presented in which pipework dynamics, including steady state friction, are presented by transmission line modelling (TLM). A semi-empirical feedback model of linearized VA dynamics has been developed and shown to be substantially correct. The model's restriction to small signals does not adversely affect investigation of perturbation growth or decay. Partial transmission line representation of the VA model with special measures for feedback allowed time-domain simulations of network perturbations. However, this approach is indirect and it was possible to convert the whole VA model to transmission lines and then reformulate the TLM scheme into a direct, quantitative stability analysis. Extension of the technique provided a means of assessing the sensitivity of the stability to simple network alterations.

The method has been programmed on an 80386 PC and successfully used on a large ventilation system. Success in the present context of dynamic stability for fluidic nuclear ventilation networks should be repeatable in other areas since the approach is applicable to any TLM-amenable system, be it fluid, mechanical, electrical or mixed.
Engineering, the Developing Career—A Personal View
Authors: Patten Professor Tom
Published: February 2007

The President refers to his early career in teaching and research and outlines some of the benefits. He identifies his involvement in offshore engineering as one major turning point in his career. It was a great opportunity for real collaboration between industry and higher education; progress usually required a multi-disciplinary approach and commitment from engineers, scientists and managers alike. Having added subsequently to his direct experience of industry, commerce and government departments and to his contacts with other professions in engineering and science he offers a few of his own thoughts on the health of smaller manufacturing companies, on the environment and on waste, each a matter critical in its own way to our future, nationally and globally.
The new Pressure Systems and Transportable Gas Containers Regulations: Part 2: Effects of the Regulations on the Users of Gas Cylinders
Authors: Irani R S
Published: February 2007

The primary aim of this paper is to highlight the major areas where changes will take place in the realm of gas cylinders and the various steps taken by the gases industry to enable a smooth transition into the future as a result of the Pressure Systems and Transportable Gas Containers Regulations (1989) which came into force on 1 January 1991.
Computer Based General Shape Description with Polygonal Harmonics and a Roughness Index
Authors: Reilly S , Clark N N
Published: February 2007

Description of particle shape is of wide importance in the engineering industries. Although the theory of polygonal harmonic shape analysis has been presented previously as a method for characterizing rugged particles, detailed computer implementation has not yet been described. Particle and object images have been digitized using a video camera and personal computer, and their harmonic persistences determined. The harmonic persistences are shown to relate to computer generated Fourier shapes with zero phase angle, but not to relate to Fourier coefficients describing rugged silhouettes. A relationship between the second harmonic persistence and aspect ratio is demonstrated, and it is verified that polygonal harmonics, combined with a surface roughness index, provide a general scheme for particle shape description as has been previously suggested.
A Study of the Metering of Free Flowing Particulate Solids Using Multi-Flight Screws
Authors: Jafari J F
Published: February 2007

Reports on multi-flight screw metering of free flowing solid particles, with side entry feed, could not be found in the available literature. But since the author worked to investigate its applicability as a seed metering mechanism for grain drills, the present work was considered essential as the first step. For this purpose, samples of 15 different free flowing particulate materials were closely sized and a test rig designed and constructed. Nine rotors of three, four, and five slots or flights were considered at speeds of 20, 40, 60, 80, and 100 r/min as desired. All experimental runs were replicated three times and the average values of the volumetric flowrates for each material, speed, and rotor were found. At the end a total of 410 data points were considered for analysis of the data based on dimensional analysis. The variable dimensionless groups were selected and analysed in such an order to produce linear relations. The overall results can be represented by the following equation:

It was concluded that metering, as described by the above equation, was predictable within the limits considered for each dimensional group studied.
The Developing Tube
Authors: Arthurton R I M
Published: February 2007

1990 marked the centenary of the City and South London Railway. The author describes how the London Underground tube railway system has developed over the past one hundred years, and the changes which have been made in its rolling stock and the train equipment during this time. During his nearly thirty-year career with the company he has been involved with design, maintenance and operation of the network, and developments in each area are outlined. He details improvements that have been made to the safety of the system, together with the management reorganization to enable the challenges of the 1990s to be faced.
Fatigue Durability of Tread-Braked Railway Wheels—on Admissible Combinations of Axle Load, Train Speed and Signalling Distance
Authors: Lundén R
Published: February 2007

A mathematical model for the prediction of relative lifetimes of railway wheels exposed to block braking under stop braking cycles is presented. Analytical and finite element thermoelastic calculations are employed together with a model for low-cycle fatigue. Durability curves are established describing limiting combinations of axle load and train speed for given combinations of signalling distance and required wheel lifetime. Application of the method is demonstrated on an existing freight car wheel which conforms to UIC standards. The numerical results should also be useful for other wheels.
The Application of Independently Rotating Wheels to Railway Vehicles
Authors: Eickhoff B M
Published: February 2007

This report describes the results of a study of the potential benefits and areas of applicability of independently rotating wheels for railway vehicles which has been undertaken by British Rail Research.
Central Line Rolling Stock—from Concept to Contract
Authors: Dobell M H , Fried O J
Published: February 2007

This paper describes the concept of the new Central Line rolling stock, its relationship with the Central Line modernization project and the steps that turned the concept into a specification and most recently into a £300M plus contract. It does not attempt to describe in detail the trains, but to document the processes that will ensure that the trains are right first time.
Electrical Systems Via Couplers
Authors: Tomlinson G W
Published: February 2007

This paper discusses the system requirements for electrical power and control information that need to be transmitted along the train and looks at some of the problems and limiting factors connected with these systems.
Towards a 100 Per Cent Performance
Authors: Ramsey P S M
Published: February 2007

A seminar on ‘Reliability, availability and maintainability’, organized by the Railway Division of the Institution of Mechanical Engineers, was held in London on 20 February 1990
All Change
Authors: Mitchell J R
Published: February 2007

The author outlines his educational background and early career before joining British Railways Research Department in 1969. He goes on to describe the new traction and rolling stock which has been developed in recent years and the major organizational changes which have taken place at British Rail to achieve greater accountability and customer focus. The author concludes his Address by describing the work that has taken place on the Channel Tunnel and future European developments such as the European High-Speed Network.
The Use of Structural Adhesives in the Construction of Rail Vehicles
Authors: Fowler J R
Published: February 2007

Conventional railway vehicles are generally fabricated using traditional welding techniques. An extensive investigation of adhesive bonding technology as an alternative is reported. A description of how an optimum adhesive was selected and the characterization of its important properties—lap shear, fatigue, shear modulus, durability and impact—is given. The crashworthiness of large bonded details is compared with similar welded constructions. The manufacturing procedure used to produce large bonded bodysides (5.8 times 2.2 m) is described. The structural testing of bonded bodyside modules is reported and compared with a traditional welded structure.

Bonded bodyside modules were incorporated into a production multiple unit. The modules had excellent finish and the unit has performed satisfactorily in passenger carrying service. Non-destructive techniques which allow disbonds to be detected during manufacture/assembly and at major service inspections are also discussed.
Laser Anemometry in Turbomachines
Authors: Ahmed N A , Forster C P , Elder R L
Published: February 2007

This paper describes how laser anemometry is particularly suited to the measurement of flows in and around turbomachinery. The operation and use of both laser Doppler and laser transit anemometry are discussed. Finally, some measurements taken at Cranfield Institute of Technology using laser anemometers are presented.
Landing Gear—the Aircraft Requirement
Authors: Greenbank S J
Published: February 2007

The trends of major landing gear design parameters are presented reflecting the developments in aircraft performance over the last two decades. These trends illustrate the likely requirements for the future and identify the differences between civil and military landing gears.

The aircraft manufacturer will inevitably demand a lower mass landing gear, increased service life and lower support costs of the product, the latter now becoming increasingly important. The method of achieving lower support costs, known as integrated logistic support, is summarized, highlighting the relevance to landing gear design.

A number of likely changes required to meet future aircraft demands are discussed and how they will test the innovation and ingenuity of the landing gear designer.

Key areas include, (a) stringent turn-round requirements demanded by aircraft operators, (b) computer control of actuation, nose wheel steering and wheel brake control systems and (c) the advent of advanced suspension systems, particularly for military STOVL and repaired runway operations.
Testing Transmission Lubricants: The Importance of Thermal Response
Authors: Olver A V
Published: February 2007

The performance of transmission systems, especially those of high criticality and specific torque capacity such as those in helicopters, depends strongly on lubricant behaviour.

However, economic load capacity evaluation of lubricants involves the correlation of test results obtained from simple tests in order to predict service performance, which is an unreliable step. In this paper the role of the thermal characteristics of the test machine is explored and the results used to resolve the apparent contradictions in the ranking order obtained from different test methods.

A simple method for calculating the bulk and surface temperatures in disc machines is given together with corresponding experimental confirmation. The performance of two lubricants that show a reversal in ranking order at a particular temperature is examined.
Testing Extreme Pressure and Anti-Wear Performance of Gear Lubricants
Authors: Alliston-Greiner A F
Published: February 2007

This paper outlines some of the problems faced by gear lubricant formulators in using standard test methods to determine the anti-wear and extreme pressure (EP) performance of their lubricants. Traditional tests for ‘load-carrying capacity’ or ‘scuffing resistance’ are reviewed and compared. A new test procedure is presented which focuses on the overall temperature performance and load-carrying capacity of the lubricant. This procedure should help in the prediction of the performance of today's advanced lubricant formulations.
Natural Frequencies of a Rotating Cable/Spacecraft System
Authors: Shippen J M
Published: February 2007

Dynamic analyses are presented of a spin-stabilized spacecraft that can be regarded as a rigid central body with several deployed cables. Firstly, the normal modes analysis is carried out of an isolated cable attached to a rigid body spinning at a constant angular velocity. This initial decomposition is reasonable as light cables attached to a massive central body behave independently as a first approximation and simplifies the derivation of the equations of motion. The three-dimensional wave equation in a rotating coordinate system is derived and solutions found using a lumped parameter approach. This analysis is novel as it presents an analysis technique to study the effect on the natural frequencies of physical characteristics (that is vibration planes containing and normal to the spin axis) and varying design parameters (that is cable length, cable density, tip mass) are considered. The study is then extended to consider the interaction of the cables and the central body for a system that is not subjected to external torques.
Life Cycle Costing and the Facts of Life
Authors: Daniel D W
Published: February 2007

The basic principles of life cycle costing (LCC) have long been recognized yet the history of subsequent achievement has been disappointing. The author believes much of this lack of progress can be attributed to the two topics discussed in this paper: the problems involved in providing credible estimates and misunderstandings concerning the utility of LCC, used in isolation, to inform decisions. Drawing an analogy with operational research suggests the need for LCC practitioners to pay particular attention to understanding the nature of the management problem being addressed and to base their estimates on empirical, and auditable, data.
Medical Engineering—The Multi-Disciplinary Challenge
Authors: Dowson D
Published: February 2007

This lecture highlights the multi-disciplinary nature of medical engineering. The author reviews various aspects in the field including artifical heart valves and total replacement synovial joints. He also considers the development of education and training and he explores the relationship between medical engineering and The Fellowship of Engineering. The author concludes that there is an immense amount of interest in the subject although more funding is needed for future development.
Muscle-Ligament Interactions at the Knee during Walking
Authors: Collins J J , O'Connor J J
Published: February 2007

A two-dimensional mathematical model of the knee is used with gait analysis to calculate muscle, cruciate ligament and tibio-femoral contact forces developed at the knee during normal level walking. Ten normal adult subjects—four females and six males—participated. The knee model is based upon a four-bar linkage comprising the femur, tibia and two cruciate ligaments. It takes account of the rolling and sliding of the femur on the tibia during flexion/extension and the changes in direction of the ligaments and muscle tendons. We considered forces transmitted by six elements: quadriceps, hamstrings, gastrocnemius, anterior and posterior cruciate ligaments, and tibio-femoral contact. The equations of mechanics can be used to determine the absolute values of only three of the knee forces simultaneously, so that twenty limiting solutions of three of the six forces were considered. A limiting solution was rejected if any of the three forces were negative, corresponding to compressive muscle or ligament forces, or tensile contact forces.

These constraints always reduced and at times removed the redundancy of the knee structures. The high incidence of predicted single muscle activity, supported by electromyography, suggested that the ligaments play a significant role in load transmission during gait. The temporal patterns of muscle and ligament activity and ligament force magnitudes were sensitive to the choice of model parameters. The analysis showed that each of four possible minimum principles of muscle selection—minimal muscle force, muscle stress, ligament force and contact force—was unlikely to be valid throughout the walking cycle.
A Biomechanical Model of the Human Spinal System
Authors: Dietrich M , Kedzior K , Zagrajek T
Published: February 2007

An experimental study of spinal biomechanics both in vivo and in vitro is difficult and often not reliable enough. The mathematical modelling and computer simulation approach is one that can be successfully applied. Modelling in this case is difficult due to the very complicated, heterogeneous nature of the object under investigation. The paper presents a biomechanical model of the spine system consisting of the spinal column (vertebrae, discs), ligaments, muscles directly and indirectly acting on the spinal column, as well as the rib-cage, abdomen and part of the pelvis. The finite element method combined with the optimization approach has been used for modelling. Typical results of these investigations are presented.
Stress Wave Effects in a Finite Element Analysis of an Impulsively Loaded Articular Joint
Authors: Anderson D D , Brown T D , Radin E L
Published: February 2007

A dynamic contact finite element formulation was used to study transient stresses in the impulsively loaded rabbit knee, an established experimental model of mechanically induced osteoarthrosis. The computations were used to test the hypothesis that stress wave propagation and reflection, from juxtarticular interfaces of material property discontinuity, could be responsible for markedly increased levels of transient local cartilage stress. The finite element results demonstrated intuitively credible stress wave propagation and interfacial reflection phenomena. However, the magnitude of these waves was not nearly large enough to appreciably alter the quasi-static stress distributions otherwise prevailing. Thus, local stress wave reflection from interfaces of modulus discontinuity (for example the cartilage/subchondral plate) probably does not contribute appreciably to the heightened tissue sensitivity to impulsive loading experimentally observed in this animal model.
Short Stem in Charnley Low-Friction Arthroplasty—A Review of 100 Cases
Authors: Stone M H , Wroblewski B M , Siney P D
Published: February 2007

One hundred cases of the Charnley low-friction arthroplasties using shorter (75–110 mm) than standard length stems, both in primary and revision surgery were reviewed. The average follow up was five years and three months. Eleven had cortical thickening that could be attributed to the predicted increase in the stresses within the femoral cortex. There were no cases of cortical thickening when the stem was 100 mm or longer. One stem in the 80–84 mm group was revised for lossening.

The findings suggest that other than cortical thickening, which has not progressed during the period of the follow-up, there is no need to fear the use of shorter stems if indicated for technical reasons and provided good stem fixation can be achieved.
Shear Properties of Articular Cartilage of a Bovine Knee Joint Subjected to Moderate and High Loads: An Experimental Study
Authors: Saxena R K , Sahay K B , Guha S K
Published: February 2007

Freshly excised bovine knee joints were subjected to oscillation under constant load on a specially designed knee joint articulating machine with the joints subjected to moderate and high loadings of 1471.5 and 2943 N respectively. Instantaneous and equilibrium shear moduli of the articular cartilage obtained from the experimental knee joints were measured on a mechanical indentor (DuPont 943 TMA) and compared with the corresponding values of the shear moduli of the cartilage obtained from the control knee joints. At moderate load, both the instantaneous and the equilibrium shear moduli exhibit significant increase in their values. However, at high load the constant shear moduli showed a decrease in its value whereas the value of the equilibrium shear modulus was observed to increase slightly.
Quantitative Mechanical Assessment of the Extraocular Muscles
Authors: Al-Hinnawi M F , Barbenel J , Al-Qurainy I A , Dutton G N
Published: February 2007

The active and passive behaviour of the extraocular muscles can be investigated by measuring the force that must be applied to rotate the eyeball when the muscles are relaxed (the forced duction test) or the force required to maintain the eyeball stationary while the contralateral eye follows a moving target (the force generation test). Apparatus and test procedures for carrying out both tests are described. Normal values and confidence intervals for the tests have been obtained and the results of muscle entrapment and palsy illustrated.
The Development of a Prototype Patella Tendon Bearing Prosthesis Using High-Density Polyethylene Piping (The Drainpipe Leg)
Authors: Meanley S
Published: February 2007

In Nepal, the few centres that offer a lower limb prosthetics service generally use a laminate of polyester resin with cotton stockinette in the manufacture of the hard socket and cosmesis. Until 1989 this was also the only process used at Green Pastures Hospital in Pokhara. In response to a materials shortage brought about by a local international trading dispute, however, a prototype patella tendon bearing prosthesis was developed using high-density polyethylene piping.

The terrain of Nepal, local walking habits, and therefore expectations of a prosthesis, differ considerably from those in the United Kingdom; hence some unusual design requirements are needed to be taken into consideration. This paper describes the progress of the design over several months and the constraints under which the work was carried out. Feedback was sought at the meeting at which the paper was presented, and would also be valued in response to this written account of the work.
Finite Element Analyses of Repaired Articular Surfaces
Authors: Wayne J S , Woo S L-Y , Kwan M K
Published: February 2007

The response to a compressive load of a repaired cartilage surface, consisting of full-thickness repair tissue adjacent to normal cartilage, was predicted by the u-p finite element method and compared to that of a normal cartilage surface under the same loading conditions. By individually varying the aggregate modulus, permeability and Poisson's ratio for the repair tissue, analyses were performed to assess the contributions of each to the changes in mechanical behaviour. In comparing the repaired to normal surfaces, the presence of a softer repair tissue resulted in increased axial and decreased radial deformations at any given time point, while a repaired surface with an increased permeability compressed more easily due to the increased fluid flow and caused equilibrium to occur sooner. For smaller Poisson's ratio, the axial deformation was not different from normal if the aggregate modulus was the same as normal; however, the radial expansion was reduced as the repair tissue experienced a larger volume change. These results indicate that the presence of repair tissue in a joint surface can have a strong influence on the mechanical behaviour of the surface.
Non-Invasive Diagnosis and Prophylaxis in Orthopaedics
Authors: Kernohan W G , Mollan R A B
Published: February 2007

In this paper some ten years of work in bioengineering is described. The central theme is non-invasive diagnosis and prophylaxis. This theme is exemplified in several interrelated sections of work which are described. The work is categorized into: modest beginnings, hip and knee vibration papers, deep venous thrombosis and cavitation in human joints. The philosophy is straightforward—to benefit patients by making harmless measurement.
Deformation of the Cement Mantle of Tibial Components following Total Knee Arthroplasty: A Laboratory Study
Authors: Finlay J B , Hardie W R , Bourne R B , Chris A D
Published: February 2007

An in vitro model has been developed to measure in-plane strains of the cement mantle, sandwiched between the tibial component and the underlying cancellous bone following total knee arthroplasty. Maximal in-plane strains occurred in the cement mantle below the contact points between the femoral and tibial components. These strains were significantly reduced by increasing the thickness of the polyethylene and even more impressively by metal backing. Eccentric loading, by as little as 5°, increased the strains in the loaded compartment by 26 per cent and decreased those in the unloaded compartment by 62 per cent. The addition of torsion to axial loading did not significantly alter the principal direct strains or the principal shear strains. Although surface-covering tibial components have been advocated, continuous support of the cortical rim did not appear to be important in reducing cement mantle strains. While other studies have emphasized the critical stresses that may occur in the polyethylene tibial components of total knee implants, this study highlights the potential for localized cement fatigue with improperly sized components or with eccentric loading.
Assessment of Pressure Drop Flowrate Relationship of Axillobifemoral Bypass Grafts
Authors: How T V , Al-Shukri S
Published: February 2007

An in vitro study was conducted to measure the pressure distributions in knitted polyester axillobifemoral bypass grafts under steady and pulsatile flow of a Newtonian fluid. The relationship between pressure drop and flowrate was determined across the outflow branches of two types of axillobifemoral grafts. Pressure losses were greater across the 90° side branch of the T-type graft than in the Y-type graft at all Reynolds numbers studied. Mean pulsatile pressure drops in the T graft were greater than those measured in steady flow at the same Reynolds number. Estimates of the likely in vivo pressure drops are made under resting and exercise flow conditions. It is suggested that the Y graft is less likely to have a significant effect on blood supply to the lower limbs, even at high blood flowrates.
The Impedance Characteristics of Fluid Power Components: Restrictor and Flow Control Valves
Authors: Johnston D N , Edge K A
Published: February 2007

Impedance characteristics of hydraulic components have a significant effect on pressure ripple levels in hydraulic circuits. These pressure ripples lead to vibration of pipework and associated fittings and are a source of unreliability and noise. This paper describes an experimental investigation of restrictor and flow control valves using a specially designed circuit. For a restrictor valve, it was found that the impedance characteristics were influenced by fluid compressibility, fluid inertia, valve vibration and downstream impedance effects. When these effects were taken into account, the valve could be modelled as a simple orifice.

The impedance characteristics of a flow control valve were found to be more complex and wave propagation within the valve fluid passageway had a dominant effect on behaviour.
Modelling, Parameter Selection and Simulation of a Single-Cylinder Four-Cycle Engine
Authors: Thompson S , Duan S Y
Published: February 2007

This paper describes the procedure involved in developing a simulation model of a single-cylinder four-cycle engine, suitable for fuel injection control system studies. In particular, the modelling procedures and methods of parameter selection, including supporting experimental work, are indicated. Responses obtained from the simulation model are then compared with those obtained experimentally from the engine. Finally, future improvements to the model are suggested.
Transmission of Vibration and Pressure Fluctuations Through Hydraulic Hoses
Authors: Longmore D K , Schlesinger A
Published: February 2007

It is demonstrated that measured relationships between the vibration and pressure fluctuation at the input and output ends of hydraulic hoses, such as would be generated by a pump and transmitted to the subsequent circuit, can be described satisfactorily by two types of wave involving differing proportions of predominantly axial motion of the hose and the contained fluid, together with bending and torsional wave motion. The values of the wave properties required to do this are presented for four representative hose constructions, and the relationship of the properties to the construction is discussed.
Mechanical Design and Control of the TUD-ESA Spherical Near-Field Antenna Test Facility at Lyngby, Denmark
Authors: Conrad F
Published: February 2007

A fully automatic spherical near-field antenna test facility designed for space applications has been implemented in the radio anechoic chamber of the Technical University of Denmark (TUD). The facility was developed jointly with the European Space Agency (ESA). In 1979 the first manually controlled facility was in operation. Later, in 1984, a second, fully automatic and improved version of the facility was implemented, and in 1985 the frequency range was extended to 40 GHz. Since then, efforts have continued to be made to improve the capabilities. The paper deals with the development, design, control and implementation of the mechanical system consisting of a new high-precision elevation over azimuth positioner and a probe tower. The facility is intended for measurements of antennas with diameters up to 6.7 m within a frequency range of 1.7–40 GHz. The measurement accuracies and some typical measurement results are described.
A Class of Decentralized Tracking Controller for Robot Manipulators
Authors: Osman J H S , Roberts P D
Published: February 2007

The tracking control of a robot manipulator in the presence of uncertainties is considered, where the robot manipulator and its actuating system are treated as a set of interconnected sub-systems with bounded uncertainties. Utilizing the local states as well as the states of the connecting sub-systems, a class of decentralized continuous non-linear feedback control law is presented for the tracking problem of the robotic system. The design of the controller is based on the deterministic approach.
Computer Simulation of a Semi-Closed-Circuit Breathing System
Authors: Tilley D G , Tomlinson S P , Livesey J
Published: February 2007

The operational performance of underwater breathing systems is currently assessed using manned and unmanned testing. Due to the complexity of these systems, it is often difficult to understand fully the observed behaviour. Computer simulation is a well-established technique in the analysis of complicated dynamic systems and is considered an ideal tool for this application. Simulation, when used in conjunction with experimental testing, promises significant advances in both the understanding and the performance evaluation of underwater breathing systems.

This paper describes a simulation study undertaken on a semi-closed-circuit breathing system. Details are included regarding the derivation and validation of the mathematical models of the system components and examples presented showing how simulation can be used as performance assessment and design tools.
Performance Optimization of an Electrohydraulic Position Control System with Load-Dependent Supply Pressure
Authors: Watton J , Al-Baldawi R A H
Published: February 2007

A proportional pressure relief valve is used to control the pressure supply to an electrohydraulic servo-valve in conjunction with a novel yet simple way of eliminating position error. This requires the measurement of the load force and a means of adjusting the supply pressure as the load force changes. The technique hinges on the need to have symmetrical underlapping of the servo-valve spool, and this then enables position error to be eliminated, the transient behaviour to be optimized, and a fortuitous improvement in power dissipated. The concept is verified by the use of a two-axis system, the main position control axis being rotated in a vertical plane, thus creating a variable load. The effect of pressure adaptation is clearly shown for slowly varying rotation of the test axis, pressure adaptation being achieved via a microcomputer interfaced between the load-sensing transducer and the proportional pressure relief valve.

The dynamic performance for rapid changes in the demanded position is studied, and it is shown how a linearized transfer function approach leads to a simple design strategy. It is shown that fluid compressibility effects are negligible owing to an appropriate choice of servo-valve spool underlap, which also leads to a robust design in terms of the closed-loop damping ratio. This leads to simplicity in maintaining optimum dynamic performance, which is then only affected by supply pressure changes which are known.
A Hybrid Model Reference Adaptive Control/Computed Torque Control Scheme for Robotic Manipulators
Authors: Maliotis G
Published: February 2007

A direct model reference adaptive controller scheme for a robotic manipulator based on the Lyapunov stability criterion is developed. The algorithm presented is based on the formulation of a plant state model that includes all the non-linear characteristics of the robot manipulator. This adaptive controller takes advantage of the structure and any known dynamics of the system in order to increase the speed of adaptation and relax the conditions required for convergence. It uses a modified Lyapunov function to derive the adaptation laws that are not dependent on the usual assumption that the time-varying plant is close to the desired time-invariant plant. The Lyapunov design guarantees asymptotic stability.
Long-Range Predictive Control Design Based on CARMA Model
Authors: Tso S K , Ma Y X , Wu J
Published: February 2007

Many different long-range predictive controllers have been proposed and investigated for almost two decades. The method presented in this paper is based on a stochastic optimal design which allows the closed-loop characteristics to be explicitly identified. The CARMA model is used instead of the more commonly used incremental parametric model. The prediction horizon or cost function index can be sized according to overall system damping requirement, and even dynamically unfavourable plants can be stabilized by adequate selection of this index. The conclusion has been borne out by extensive simulation tests, and representative results are presented in the paper.
The Influence of Control System Design on the Dynamic Response Characteristics of Thermal Power Plants
Authors: Carvalho F L , Conradie F H D , van Zyl L T , Croft D G , Kuerten H , McDyer F J
Published: February 2007

The dynamic response characteristics of thermal power plants identified by power output versus time are influenced by fuel type, boiler and turbine designs, and also by the overall unit control arrangements. These factors influence significantly how a unit responds in meeting scheduled and unexpected demands imposed by the grid system to which it is connected. The paper presents typical stored energy, thermal inertia and unit responses as measured on various types of thermal power plant and control configurations for reheat units in the output range 120-800 MW, burning coal, oil and gas, in various countries, namely Australia (AUS), Germany (D), Denmark (DMK), United Kingdom (GB), Ireland (IRL), Japan (J) and South Africa (RSA).
Use of Classical Control Techniques to Stabilize the Electrical Dynamics of a Highly Unstable Road Load Simulator
Authors: Stringer I A , Bullock K J
Published: February 2007

The open-loop transfer function of a complex Ward-Leonard dynamometer system was derived from an analysis of the behaviour of the individual components. The resulting model, which was in good agreement with the open-loop performance of the system, was used to simulate the behaviour of the closed-loop system; this indicated that the system would be unstable.

Classical control theory was used to analyse the performance of a number of stabilizing control strategies, and root loci plots, Bode diagrams and Nichols charts were used to assess the resultant performance. A proportional-plus-integral controller combined with lead compensation was predicted to provide acceptable control. The performance of the system with this controller installed was found to satisfy the design requirements of speed of response, limited overshoot and zero steady-state error.
Comparative Implementation Studies of Five Adaptive Control Algorithms on a Class 1 Manipulator
Authors: Stoten D P , Hodgson S P
Published: February 2007

The paper compares the results of implementing five well known adaptive algorithms on the motion control of a planar revolute axis manipulator. The main emphasis is on the experimental results, and on the relative efficacy of each algorithm. However, we also draw comparisons of the structure of the algorithms, and the corresponding implications for discrete-time implementations.

The main conclusion is that the decentralized version of the minimal control synthesis (MCS) algorithm of Stoten and Benchoubane (1, 2) resulted in excellent model-following, with relative noise insensitivity and minimum flops per sampling interval. MCS is classed as a direct adaptive controller (3). The two other direct adaptive controllers of Seraji (4) and Oh and Jamshidi (5) did not perform as well as MCS; model-following was not so close, noise was more of a problem, and the implemented forms were more complicated. The indirect adaptive controllers of Craig (6) and Stotine and Li (7) produced virtually identical results; the model-following was excellent, but noise and parameter convergence problems were evident. The indirect adaptive controllers also suffered from the necessity for plant parameter estimation.
A Transputer Based Adaptive Control System
Authors: Anderson A J
Published: February 2007

The paper considers the application of a multiple processor system to adaptive control. The system is based on the Inmos T800 floating point microprocessor. The adaptive system is structured in three levels: adaptive controller, parameter estimator and system supervisor.

The multiple processor system is intended to act as an integrated environment for the initialization, analysis and supervision of an adaptive controller. It has useful commissioning tools and more intelligent controller management functions than are available with commercial adaptive controllers. A supervisor or coordination level is added to supervise the adaption and control levels in order to improve the applicability, robustness and integrity of the controller in real-time applications. An example is considered and the performance of the system is shown to be enhanced by the many functions within the supervisor.
Probabilistic Models for Uncertainty Management in Expert Systems with Applications to Fossil Power Plants
Authors: Valverde A L J , Gehl S M
Published: February 2007

Human experts and decision makers must typically plan and act without the benefit of complete knowledge and information. In the theory and application of expert systems, uncertainty in human knowledge and reasoning must be effectively managed in order for such systems to be successful in complex, real-world domains. In this paper two probabilistic models for uncertainty management in expert systems are considered: (a) Bayesian probability theory and (b) Dempster-Shafer belief theory. The conceptual foundations of each theory are first summarized and are then applied to a typical diagnostic inference problem drawn from the fossil plant performance area. The advantages and disadvantages associated with each approach are then discussed, concluding with some general guidelines for selecting an appropriate uncertainty paradigm for fossil power plant applications of diagnostic expert systems.
Ohaaki Power Station: Geothermal Development in New Zealand
Authors: Tokeley A H , Brown D P
Published: February 2007

The recent geothermal power station development at Ohaaki, New Zealand, is discussed, highlighting the advances in both the technology and environmental acceptability of such plant since the pioneering development at nearby Wairakei. Development strategies for the geothermal field and major design decisions relating to the power station and steamfield systems are outlined and the systems themselves are briefly described.
Inspecting Nuclear Pressure Vessels: The Conundrum of Minimizing Risk
Authors: Östberg G
Published: February 2007

The probability of a sudden, massive release of radioactivity from a light-water nuclear reactor through a breach of the containment is assessed on the basis of statistical data which partly consist of subjective estimates. This breach refers to the existence of crack-like defects remaining after a non-destructive examination of the main pressure vessel surrounding the reactor core. Two studies have recently been made of such sources of information about the effectiveness of non-destructive examination of pressure vessels with respect to defects. The results of these studies indicate that the data used as input in the probabilistic calculations do not possess the reliability that might be assumed from the assessments. This type of failure should therefore no longer be considered a de minimis case. In the present review the overconfidence in the efficiency of non-destructive examination is discussed from psychological, sociological and political science points of view. It is concluded that ingrained professional assumptions and values seem to be the main reason for the trust in the technology of inspection. However, there are also psychological constraints that can be understood only in their social and political contexts.
Charge Stratification in a Spark Ignition Engine
Authors: Green R K , Zavier C C
Published: February 2007

The effect of charge stratification on lean mixture combustion in a Ricardo E6 single-cylinder four-stroke reciprocating engine has been investigated. To do this, a commercially available spark plug was modified so that small amounts of pure methane gas could be injected, via the spark electrode, into a lean mixture within the combustion chamber prior to ignition. The effect on engine performance of variations in the methane injection process were analysed.

The research has led to the following conclusions:

1. The lean limit of a homogeneous air-fuel mixture is extended by this relatively simple charge stratification process. 2. The effectiveness of charge stratification is most noticeable at lean air-fuel ratios in terms of improved brake specific fuel consumption. 3. Unburnt hydrocarbon emission levels are higher with the stratified charge process when compared to normal homogeneous mixture operation. 4. Carbon monoxide levels with stratified charge combustion are almost the same or a little lower than normal operation at the leanest air-fuel ratios.