bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.
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.
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.
The Development and First Commercial Application of an Innovative Diesel Engine Based Cogeneration System
Authors: Nash F 
Published: February 2007

This paper covers the development of a cogeneration (combined heat and power) system based upon a compression ignition, reciprocating, internal combustion engine and a standard three-pass economic shell-and-tube industrial boiler as well as the first commercial application of the system. An innovative feature of this cogeneration system is that additional fuel is burnt to utilize the free oxygen in the engine exhaust gas (a practice common with gas turbines but rarely attempted with reciprocating engines) to provide a significant, fuel-efficient and easily variable increase in the high-quality heat, that is steam, output from the system. The initial development work was done in 1983 using heavy fuel oil as the fuel to both engine and burner, while the first commercial application in 1988 utilizes a dual-fuel engine (gas and diesel oil pilot or diesel oil) and dual firing of the exhaust gas duct burner with gas or diesel oil.
Development of European Gas Supply and Demand and Prospects for Gas Use in Power Generation
Authors: White N 
Published: February 2007

Demand for natural gas in Europe is expected to grow rapidly, particularly for use in power generation, as a result of technological developments and regulatory action to protect the environment. While there is no shortage of gas reserves to meet this potential demand, there is uncertainty over how rapidly such reserves can be developed and marketed, and at what level of cost. It seems probable that incremental gas supplies will be available only at higher prices than those being paid today, as a result of rising gas supply costs. However, it would appear that gas prices can rise further before other fuels become more commercially attractive in the power generation sector.
Decommissioning of Nuclear Reactor Systems
Authors: Large J H 
Published: February 2007

The decision-making process involving the decommissioning of the British graphite-moderated, gas-cooled Magnox power stations is complex. There are timing, engineering, waste disposal, cost and lost generation capacity factors and the ultimate uptake of radiation dose to consider and, bearing on all of these, the overall decision of when and how to proceed with decommissioning may be heavily weighed by political and public tolerance dimensions. These factors and dimensions are briefly reviewed with reference to the ageing Magnox nuclear power stations, of which Berkeley and Hunterston A are now closed down and undergoing the first stages of decommissioning and Trawsfynydd, although still considered as available capacity, has had both reactors closed down since February 1991 and is awaiting substantiation and acceptance of a revised reactor pressure vessel safety case. Although the other first-generation Magnox power stations at Hinkley Point, Bradwell, Dungeness and Sizewell are operational, it is most doubtful that these stations will be. able to eke out a generating function for much longer. It is concluded that the British nuclear industry has adopted a policy of deferred decommissioning, that is delaying the process of complete dismantlement of the radioactive components and assemblies for at least one hundred years following close-down of the plant. In following this option the nuclear industry has expressed considerable confidence that the decommissioning technology required will he developed with passing time, that acceptable radioactive waste disposal methods and facilities will be available and that the eventual costs of decommissioning will not escalate without restraint.
Cutting Tool Selection: An Intelligent Methodology and its Interfaces with Technical and Planning Functions
Authors: Maropoulos P G 
Published: February 2007

This paper presents a new cutting tool selection methodology, namely the intelligent tool selection (ITS), which covers the whole spectrum of tool specification and usage in machining environments. The selection process has five distinct levels and starts by deriving a local optimum solution at the process planning level, which is progressively optimized in the wider context of the shop-floor. Initially, multiple tools are selected for each machining operation and tool lists are formed by sorting selected tools in order of preference. The second selection level provides a tooling solution for a component by considering all the operations required as well as the characteristics of the machine tool. The selected tools are then rationalized by forming a set of tools for machining a variety of components on a given machine tool at level 3 and by increasing the use of common and standard tools within a group of machines at level 4. Finally, the fifth level aims at reducing tool inventory by classifying existing tools into categories according to their usage and is also used for introducing new tools into the manufacturing system. The selection method allows the implementation of the minimal storage tooling (MST) concept, by linking the ordering of new and replacement tools to production control. ITS also uses the concept of tool resources structure (TRS), which specifies all tooling resources required for producing a component. By using the framework provided by ITS, TRS and MST it can be shown that tooling technology interfaces with diverse company functions from design and process planning to material/tool scheduling and tool management. The selection methodology results in higher utilization of tools, improved efficiency of machining processes and reduced tool inventory.
The Politics of Industry
Authors: Warren Kenneth 
Published: February 2007

From a career in the aeronautical and electronics industry, rising from the shop floor and university to management, Kenneth Warren entered Parliament in 1970. During his time in Parliament he has been Chairman of the Conservative Back-Bench Aviation Committee and of the Western European Union's Science and Technology Committee. For four years he was Parliamentary Private Secretary to Sir Keith Joseph in the Department of Trade and Industry and then Education and Science. Currently he is Chairman of the British Russian Parliamentary Group as well as the Select Committee on Trade and Industry. Having visited some eighty countries, led parliamentary delegations overseas on a number of occasions and contributed papers at technical conferences in the United Kingdom, the United States, Holland, France, Japan and Hungary, he has a world-wide interest in the development of engineering and markets for technology. Communication between industry and politics and vice versa is not at the level of quality required in a major supplier/customer relationship. The author will develop a thesis on how this interface can be eroded. He will base his lecture on a background of international experience in politics and industry, including the Chairmanship of the Select Committee on Trade and Industry and as one of the four qualified engineers in the House of Commons.
Parametric Minimum Film Thickness Performance of an Elastic Big-End Bearing under Inertial Load
Authors: Aitken M B , McCallion H 
Published: February 2007

Big-end bearing design has, in the past, been well served by design charts. However, in more recent times, simple design-level information has not kept pace with developments in bearing analysis. This paper presents simple parameterizations of the effects of con-rod distortion on dynamic big-end minimum film thickness performance. Non-dimensionalization of cyclic minimum film thickness, film mechanism transitions, bearing flexibility and inertial load enabled quantitative tribological measures of elastic geometry to be developed. This characterization, ratified against corresponding full analyses, provides a useful new insight into elastic con-rod bearing design, something hitherto based on experience and intuition.
Externally Pressurized Hemispherical Fibre-Reinforced Plastic Shells
Authors: Blachut J , Galletly G D 
Published: February 2007

The results of external pressure tests on ten 0.8 m diameter torispherical shells made from FRP (fibre-reinforced plastic) were discussed in a recent paper by the authors. In the present paper, the results of similar tests on six hemispherical FRP shells are given. Four of the hemispheres were made from single sheets of woven pre-preg (three of carbon-fibre-reinforced plastic and one of glass-fibre-reinforced plastic): two of those made from carbon-fibre-reinforced plastic (CFRP) were petalled, that is they were made by butt-jointing together pieces of composite cloth. The diameter-average thickness (D/tav) ratios of the hemispherical domes varied from 66 to 108. The BOSOR 4 program was used to predict the stresses in the composite shells and their buckling pressures; the Tsai-Wu equation (in stress space) was utilized for the material failure criterion. For all the shells in this investigation, the controlling failure mode appeared to be first-ply failure (FPF). The latter is, of course, influenced by the compressive strength of the composite. Assuming a reasonable value for this (for example 570 N/mm2 for CFRP) gave ratios of Pexpt/PFPF which were in the range 1.05–1.19. In all cases, the experimental result was higher than the theoretical prediction, that is it was on the safe side. The authors measured the compressive strength of the CFRP composite experimentally. They obtained values in the range 510 ± 100 N/mm2. These were less than values obtained at Imperial College (664 ± 44 N/mm2). At the moment, it is not known why this wide variation in compressive strength was obtained. More work needs to be done on this aspect of the problem. Each of the butt-jointed CFRP hemispherical domes was weaker than its unjointed counterpart. In part, this is due to the increase in thickness of the unjointed hemispheres near the clamped edge, where the failures originated. With the CFRP torispherical domes, the failure location was at the spherical cap/knuckle junction (that is away from the clamped edge) and the butt-jointed torispherical dome turned out to be stronger than its unjointed counterpart. The 30-ply CFRP hemisphere (D/tav = 66) was 1.4 times as strong as the 36-ply GFRP hemisphere (D/tav = 73). In addition, the 30-ply CFRP hemisphere had the same collapse pressure as a geometrically similar welded steel hemisphere which had D/t ≈ 113 and a = σYP = 645 N/mm2. The CFRP dome would be much ligher than the steel one, in the ratio 1:2.8.