bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Implementation Studies of the Minimal Control Synthesis Algorithm on a Class 1 Manipulator
Authors: Stoten D P , Hodgson S P
Published: February 2007

The minimal controller synthesis (MCS) algorithm (1) is a novel form of adaptive control, which has been shown to be particularly effective in a number of diverse areas (2). In particular, the problem of general manipulator control, using MCS, has been successfully analysed and simulated in previous works (3, 4). The intention of this paper is to provide the first implementation results of MCS upon a manipulator. It is shown that MCS produces results that are far superior to those produced by an equivalent conventional (linear) control algorithm.
A Design Study of a Self-Organizing Fuzzy Autopilot for Ship Control
Authors: Sutton R , Jess I M
Published: February 2007

This paper describes the development of a self-organizing fuzzy autopilot for controlling the non-linear yaw dynamics of a warship. Simulation results are presented which demonstrate the autopilot's ability to operate over a wide range of ship speeds and course changes. An improved design methodology is also proposed which replaces the exhaustive experimental analysis normally associated with the formulation of self-organizing controllers.
Computed-Torque and Variable-Structure Multi-Variable Control of a Hydraulic Industrial Robot
Authors: Habibi S R , Richards R J
Published: February 2007

The paper considers the application of a mathematical model proposed for the control of hydraulic robots with large supply pressure. The model of the Workmaster hydraulic robot, formerly manufactured by Thorn EMI Robotics, is simplified and used for the computed-torque and variable-structure control applications both in simulation and in practice. The model-based controllers are examined, and new insight is gained into the working of hydraulic robots. The use of pressure feedback for compensating the supply-line dynamics is practically demonstrated.
An Iterative Learning Controller for Hydraulic Servo-Systems Subjected to Unknown Disturbances
Authors: Park H J , Cho H S
Published: February 2007

Many processes such as machining, injection-moulding and metal-forming are usually operated by hydraulic servo-systems. The dynamic characteristics of these systems are complex and highly non-linear and are often subjected to the uncertain external disturbances associated with the processes. Consequently, the conventional approach to the controller design for these systems may not guarantee accurate tracking-control performance. Taking into account the repetitive nature of the operations in those processes, a discrete iterative learning control algorithm is proposed to realize an accurate hydraulic servo-system regardless of the uncertainties and the external disturbances. In the algorithm, the control input sequence for the next operation is determined by utilizing the tracking error, as well as information on the dynamic characteristics obtained from the past operations, so that the output trajectory tracks the given the desired trajectory as closely as possible. To investigate a gradual improvement of tracking performance in consecutive operations, the proposed algorithm was implemented on a hydraulic servo-system. A series of experiments was performed for the position-tracking control of the system subjected to external disturbances. The experimental results show that, regardless of inherent non-linearities and disturbances, an accurate tracking-control performance is obtained using the proposed learning control algorithm characterized by recursive operations.
In-Situ Measurement of the Wavespeed and Bulk Modulus in Hydraulic Lines
Authors: Johnston D N , Edge K A
Published: February 2007

The dynamic performance of a hydraulic system is dependent on the fluid bulk modulus, which can be affected by several factors including air release and pipe compliance. A technique is described for the in situ measurement of the speed of sound from which the bulk modulus may be evaluated. It entails analysis of pressure ripple recorded at three locations in the hydraulic line. Measured values of the bulk modulus in high-pressure pipes were found to be close to the isentropic tangent bulk modulus predicted from the fluid manufacturer's data.
Component Oriented Modelling of a Valve Controlled Asymmetric Cylinder Drive Using a Generalized Formulation for Model Linking
Authors: Leaney P G
Published: February 2007

A computer aided design facility for the analysis and simulation of hydraulic servo-systems is being developed, and this work has highlighted the lack of a suitable component oriented model for the asymmetric cylinder drive. Current literature characterizes the linking between the valve and the asymmetric cylinder by the service line pressures and flows which together represent up to four variables. This paper outlines a simplified approach by defining and utilizing generalized definitions of load flow and load pressure so that adequate linking is made possible by the two simple product variables of power. This enables a model to be produced in a way that is directly analogous to that of a symmetric cylinder drive. Particular difficulties associated with spool operation in the underlap region and with laminar leakage modelling are addressed. The model thus provides an intuitive insight into the particular control problems associated with asymmetric cylinder drives when controlled by a symmetric four-way valve, a combination found in many applications. Computer generated results are compared with observed results from a test rig. A steady state model solution is shown to emulate the steady state characteristics of the drive. A dynamic model solution, via simulation, is shown to correspond well with observed response. Both open- and closed-loop responses are tested. The characteristic of an asymmetric cylinder to demonstrate a higher gain and lower damping when extending (compared to retracting) is clearly evident in the results. The generalized definitions demonstrate potential for application in a wide range of analysis techniques.
Performance Study of a Mixed Flow Impeller Covering an Unsteady Flow Field
Authors: Sarkar S
Published: February 2007

The results presented here are part of a detailed programme measuring the aerodynamics of a high specific speed mixed flow pump impeller over a wide range of operating conditions, including its behaviour in the unsteady stalled regime. The aim is to elucidate the physics of the flow through such an impeller. The noticeable features are the formation of part-span rotating stall cells having no periodicity and organized structure at reduced flow and also the shifting positions of reversal flow pockets as the flowrate changes. Measurements of loss and its variation with span-wise positions and flowrates enable the variation of local efficiency to be determined. The overall flow picture is similar to that expected in an axial flow impeller, though the present impeller displays a narrow stall hysteresis loop almost right through its operating range.
The Design of a Method and Equipment for Decommissioning the WAGR Pressure Vessel and Insulation
Authors: Thompson G
Published: February 2007

The paper is a comprehensive design study and describes a method for decommissioning the Windscale advanced gas-cooled reactor (WAGR) pressure vessel and insulation. The design of equipment to carry out the required operations is also given. The structure of the pressure vessel and insulation and its residual activity are described and assessment criteria are proposed to judge the suitability of possible decommissioning methods. Various ideas are then considered and compared using the assessment criteria. The most promising solution is developed and general arrangement drawings of equipment are given. A reserve method, using different technology, is identified in case the first method fails due to unforeseen circumstances. The method has been adopted for development in the WAGR decommissioning programme.
A Prescribed Wake Aerodynamic Model for Vertical Axis Wind Turbines
Authors: Basuno B , Coton F N , Galbraith R A
Published: February 2007

A new aerodynamic model for the prediction of vertical axis wind turbine performance is introduced. The model is fully three dimensional and is derived from consideration of both momentum and vortex theories. In the calculation process the turbine wake is modelled by a series of shed and trailing vortices. The overall shape of the wake, however, is determined from momentum theory. Comparison is made between the new model and a free vortex method. Although the accuracy levels of the two techniques are equivalent, the prescribed wake model is more than two orders of magnitude faster. The prescribed wake model is also shown to compare well with field data. Finally, the future development of the model is discussed.
Computer Aided Assembly Process Planning
Authors: Henrioud J M , Bourjault A
Published: February 2007

A method allowing a systematic generation of assembly plans for mechanical products is presented. It involves a product modelling that includes non-assembly relevant features like labelling, checking, etc. Assembly plans are represented by assembly trees and are produced through interactive software written in PROLOG. An analysis of assembly constraints is also presented with a distinction between operative constraints dealing with the feasibility of the operations involved in the different assembly plans and the strategic constraints dealing with the global structure of the plans. An automatic transformation of the resulting assembly plans into one or several precedence graphs is given as well as a generalization of the classic precedence graphs in precedence hypergraphs able to represent disjunctive precedence conditions.
Creep Feed Grinding Of Advanced Ceramics
Authors: Rezaei S M , Suto T , Waida T , Noguchi H
Published: February 2007

Experimental investigation of creep feed grinding of ceramics and their advanced composites is described. Among silicon carbide, zirconia, alumina and silicon nitride, the latter was found to be the most difficult to grind ceramic. Fibre-reinforced silicon nitride was ground in three directions to the fibre. It is shown that grinding normal to the fibre direction required the highest grinding power. However, this was still half of the power required for pure silicon nitride. By contrast, silicon nitride that was reinforced with silicon carbide whiskers required considerably more energy to be ground. Aluminium-reinforced alumina, as expected, was easier to grind than pure alumina. Measurements of the surface roughness of all ground workpieces are also presented.
Improving the Fatigue Resistance Of Cold Forging Tools by Fe Simulation and Computer Aided Die Shape Optimization
Authors: Geiger M , Hänsel M , Rebhan T
Published: February 2007

It is the intention of the present article to point out a new method for computer aided tool optimization as part of computer integrated tool manufacturing. Based on the results of finite element (FE) analysis and subsequent tool failure simulation, it is possible to optimize the FE model of a tool already at the stage of construction, in order to enhance the service life and process reliability. The permissible degree of freedom for any shape correction, of course, is mainly limited by constructive constraints of the tool and the properties of the material flow during the extrusion process. Thus the resulting optimized geometry has to he considered as a possible constructive alternative. However, analytical as well as practical solutions already show that a parabolical or elliptical curved surface contour, replacing a regular radius, not only improves the fatigue resistance but may have a positive influence on material flow behaviour, friction forces and resulting tool loads as well (1).

The influence imposed on the material flow by the geometrical modification of the die shape will be clarified in future by the results of FE process simulation. A renewed simulation run, employing the optimized shape, may be conducted immediately after the optimization process. Along with current material research, the simulation of tool failure based on the finite element method (FEM) analysis of forging techniques (FE process simulation) therefore represents a promising direction for future developments (2–4).
Manufacturing Code Generation in a Product Model Environment
Authors: Corrigall M J , Lee M K , Young R I M , Bell R
Published: February 2007

In recent years the integration of design and manufacture software applications has received significant research effort as it has major potential to improve industrial performance. Product modelling is becoming accepted as the mechanism by which a central source of product data can be captured to provide an integrating mechanism between a range of design and manufacture functions. This paper describes the exploration of a product model environment as an integration mechanism for a number of manufacturing code generation functions, namely a machine planner, an inspection planner and a feedback system. These provide an integrated preproduction proving facility. The software implementation concentrates on the machining and inspection of two-and-a-half-dimensional prismatic components using a three-axis vertical machining centre and a coordinate measuring machine.
Performance Improvement Of Shrink-Fitted Assemblies by Surface Strengthening
Authors: Ramamoorthy B , Radhakrishnan V
Published: February 2007

Interference fits are widely used in engineering applications. Many methods have been tried out to improve the strength of interference fits by improving the quality of the mating surfaces. An experimental investigation was carried out to study the strength of the assemblies after ball burnishing the shafts, which improves the surface finish and also imparts the surface strength by way of improving the hardness and residual compressive stresses. The assemblies were soaked for different duration times at elevated temperature and then the axial load-bearing tests were carried out in a Universal testing machine. The surface strengthening of shafts by burnishing and ageing of assemblies at high temperature resulted in considerable improvement of strength of the interference fit assemblies. This paper discusses the experimental investigations in detail and analyses the strength obtained from them.
Investigation of the Cogging Process by Three-Dimensional Thermo-Viscoplastic Finite Element Analysis
Authors: Cho J R , Park C Y , Yang D Y
Published: February 2007

The purpose of cogging in open-die press forging is to maximize the internal deformation for better structural homogeneity and centre-line consolidation in the core of the ingot. A three-dimensional thermo-viscoplastic finite element analysis is carried out for the non-isothermal cogging process in order to study the distribution of hydrostatic stresses, effective strains and temperature of the ingot and the die during the process. In the simulation, V-die and flat-die are employed for computation. A circular ingot of body weight 160 ton is subjected to cogging simulation and the effects of cogging parameters, such as die configuration, die width, temperature gradient, height reduction and draft design, are compared between two types of dies. Thus favourable working conditions are suggested for better and more desirable product quality.
In-Grasp Robotic Fine Motion with Frictionless Elastic Point Contacts
Authors: Ghafoor A , Kerr D R
Published: February 2007

This paper discusses the form-closure robotic grasping of a rigid object and shows how fine motion of the grasped object may be induced. Preloads are applied along point contacts, a knowledge of whose elastic properties are necessary to overcome statical indeterminacy in the grasp, and whose properties can be exploited to allow the induced fine motion. Appropriate values of these preloads can be derived so as to maintain the grasp against external loads and to induce predefined fine motion to the object. Where a defined fine motion cannot be exactly induced, a best approximation can be found. The analytical approach is supported with examples.
Vibrations of Circular Cylindrical Shells under External Water Pressure
Authors: Ross C T F , Johns T , Stanton R M
Published: February 2007

A theoretical and an experimental investigation was made on the vibration of three machined circular cylindrical shells under external water pressure. The theoretical investigation was based on the finite element method, where the shell was modelled by a truncated thin-walled conical shell element and the surrounding fluid by an annular element which had a cross-section in the form of an eight-node isoparametric quadrilateral.

Comparison between theory and experiment was good and showed that the resonant frequencies decreased with an increase in the externally applied water pressure.
Numerical Simulation of the Modified Two-Temperature Horizontal Bridgman Growth of Gallium Arsenide Crystals inside a Quartz Boat
Authors: Hsieh M H , Chieng C C
Published: February 2007

A three-dimensional simulation of the modified two-temperature horizontal Bridgman growth of gallium arsenide crystals has been developed. The computer model solves time-dependent, Navier-Stokes equations with a Boussineq approximation by the finite difference method. A new model of nodal latent heat is adopted for melting and freezing processes. The interface of solid-liquid phases as well as flow and temperature fields of both phases are obtained. The simulation finds that the furnace pulling rate and the heat-loss prevention arrangement has an impact on the shape of the interface. The computed solidification fronts agree with the experimental data successfully. The radiation heat loss in the process plays a major role in the heat-transfer mechanism, which has been taken into consideration to obtain the correct trend for the simulation.
Engineering at the Interface
Authors: Dowson D
Published: February 2007

The President illustrates the challenges facing engineers at a number of interfaces between established disciplines, experiences and structures. An account of influences on his own early education and training are followed by descriptions of his fascination with the characteristics of thin films of lubricant at the interfaces between moving parts of machine components and body masses in the human frame. Developments in engineering education, particularly in relation to the promotion of interdisciplinary subjects and the opportunities for students to interface with overseas institutions in an international form of engineering education are outlined. The important interfaces between industry, the universities and the professional institutions in relation to education, training and research are identified as essential foundations for the promotion of a research and knowledge led competitive industrial base for the twenty-first century.
A Theoretical Account of Impeller Trimming of the Centrifugal Pump
Authors: Tsang L M
Published: February 2007

This paper gives an account of impeller trimming of the centrifugal pump. The depth of cut affects not only the head H but also the flow Q.
Computer Simulation of a Variable Fill Hydraulic Dynamometer Part 3: Closed-Loop Performance
Authors: Hodgson P G , Raine J K
Published: February 2007

An engine and hydraulic dynamometer system is dynamically modelled with two different control systems. The closed-loop system behaviour is studied for a hydromechanical back-pressure water outlet valve and for an electrohydraulic servo-controlled water outlet valve. This is an extension of the open-loop dynamic model of Part 2, which incorporates the mathematical model of the torque absorption processes in a variable fill Froude-type hydraulic dynamometer presented in Part 1.

The models are based on a system of first-order differential equations which are solved numerically using an Adams predictor corrector method. Both the analogue hack-pressure valve and digital servo-controlled valve are accurately simulated. In both cases the influence of the dynamic dynamometer model on the transient response is apparent. Variation in digital control system parameters across the operating envelope illustrates the non-linearity of dynamometer response. The computer model and experimental results are compared and implications of the closed-loop behaviour discussed.
The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—Isoviscous Behaviour
Authors: Hooke C J
Published: February 2007

In most line contacts, the film thickness can be adequately determined using a quasi-static analysis. The one exception appears to occur when the direction of entrainment changes. Here, the quasi-static approach predicts that the film will fall to zero while, in practice, there will always be a finite clearance between the surfaces. It was shown in a previous paper that this minimum clearance depends upon the rate of change of entrainment velocity, and limit expressions for the film thicknesses in the four regimes of lubrication were developed.

The present paper examines the transition between the rigid-isoviscous and the elastic-isoviscous regimes and determines how the minimum film thickness behaves in this transition zone.
A Comparison between Active and Semi-Active Control of a Simple Vibrating System
Authors: Brennan Lieutenant M J
Published: February 2007

A theoretical comparison between fully active and semi-active vibration control applied to a simple vibrating system is presented. With the advent of modern transducers and signal processing equipment, control of vibration by active rather than passive means is a practical possibility. There are many ways of implementing such control systems, and this paper discusses and compares a fully active and a semi-active system used to reduce the transmissibility of a single-degree-of-freedom system. The paper concentrates on the physical limitations of such active vibration control systems and highlights and discusses the important physical parameters.
A New Methodology for Rapid Synthesis of Function Generators
Authors: McGarva J R , Mullineux G
Published: February 2007

This paper presents the application of a new methodology for the rapid synthesis of a single-degree-of-freedom function generating linkages. Harmonic analysis and normalization are used as a means of evaluating linkage performance. The performance information for a large number of linkage types and dimensional variants are stored in a software-based library. A means whereby this library can he searched for linkages to meet prescribed performance criteria is discussed. The use of an optimization technique to ‘fine tune’ the library selections is introduced. Finally, an example of the use of the methodology is given for the synthesis of a linkage required to reproduce a particular performance requirement.
Running-In and the Enhancement of Scuffing Resistance
Authors: Kelly D A , Barnes C G , Freeman R W , Critchlow G W
Published: February 2007

Twin-disc tests in microelastohydrodynamic lubrication (micro-EHL) confirm that prior running-in at lower sliding speed enhances load and temperature at scuffing. Examination of surface oxidation and smoothing gives a new insight into the running-in process and suggests that the latter is the dominant effect. Restatement of the operating conditions in terms of non-dimensional groups that take into account the current roughness of the surfaces shows there to be little difference at scuffing.
Spatial Repeatability of Dynamic Tyre Forces Generated by Heavy Vehicles
Authors: Cole D J , Cebon D
Published: February 2007

Road damage due to heavy vehicles is thought to be dependent on the extent to which lorries in normal traffic apply peak forces to the same locations along the road. A validated vehicle simulation is used to simulate 37 leaf-sprung articulated vehicles with parametric variations typical of vehicles in one weight class in the highway vehicle fleet. The spatial distribution of tyre forces generated by each vehicle is compared with the distribution generated by a reference vehicle, and the conditions are established for which repeated heavy loading occurs at specific points along the road. It is estimated that approximately two-thirds of vehicles in this class (a large proportion of all heavy vehicles) may contribute to a repeated pattern of road loading. It is concluded that dynamic tyre forces are a significant factor influencing road damage, compared to other factors such as tyre configuration and axle spacing.
A New Constant Pressure Model for N-Branch Junctions
Authors: Corberán J M
Published: February 2007

Branch junctions are very frequently found in the intake and exhaust systems of multi-cylinder engines and they represent some of the most complex boundary conditions for wave action models. This article deals with the way of modelling a junction of N branches. Firstly, a completely new view of the general problem is presented, stating the number of closing equations that are required to obtain a well-posed problem and what kind of equations they should be. Secondly, the constant pressure theory proposed by R. S. Benson is revised from this new standpoint, showing that besides the assumption that the pressure is the same at every branch end, a second set of closing equations has to be added to the global system, and how the selection of this set is arbitrary. Then two new approaches for this second set of closing equations are proposed, analysed and compared with Benson's original theory. Finally, one of them—the assumption that the total enthalpy for all the outgoing flows is the same—is proposed to close the problem, constituting with the constant pressure hypothesis a new constant pressure model for N-branch junctions.
An Appraisal of a Continuously Variable Transmission System for Possible Application to Vehicle and Industrial Drives
Authors: Dorey R E
Published: February 2007

There is strong interest in continuously variable transmission systems of vehicle and industrial drives. They offer the potential for improved matching between the prime mover and load, together with possibilities for increased performance and more energy efficient operation. Many continuously variable transmissions have been proposed over the years, but few have received the serious consideration necessary to bring them to market prominence. This paper is concerned with the evaluation of a device that has reached a prototype stage, but would need significant investment of resources to advance its development.
Modelling of the Wall Jet in a Direct Injection Diesel Engine
Authors: Desantes J M , Lapuerta M , Salavert J M
Published: February 2007

As a part of a phenomenological model, a method for simulating the wall/jet interaction in a direct injection diesel engine is proposed. The method is based on the application of the momentum conservation equation in the different directions in which the wall jet is spread, and takes into account both the interaction with the combustion chamber geometry and with swirl. It takes as initial conditions the results of calculating the free jet, which is divided into packages. The predictions provide good agreement with those by other researchers.
Investigation of Vaned Diffusers as a Variable Geometry Device for Application to Turbocharger Compressors
Authors: Jiang P M , Whitfield A
Published: February 2007

The potential of guide vanes as a variable geometry device, placed in the conventional vaneless diffuser, to extend the operating range of a turbocharger compressor is investigated. Vaned diffusers are not normally employed in turbocharger applications as the consequent reduction in operating range is more damaging than the beneficial improvement in peak efficiency and pressure ratio. The variable geometry concept considered here is primarily one in which the guide vanes are introduced at the near surge flow conditions. The leading edge vane angle is set to accept the highly tangential flow at the near surge conditions, and the vane is then used to guide the fluid towards the radial direction in order to reduce the long flow path through the diffuser. Four types of vane arrangements are considered: (a) 12 and 6 full length vanes, with inlet vane angles of 75° and 80°; (b) 6 short inlet vanes to give a high aspect ratio; (c) 12 and 6 short vanes located in the outer half of the vaneless diffuser passage; and (d) double-row vane rings. It is shown that short vanes deployed at the diffuser outlet not only improve the efficiency and pressure ratio but also extend the high flow operating range. Further, the introduction of short inlet vanes with an inlet angle of 80° improves the peak pressure ratio and efficiency, and extends the near surge operating range.
The Role of the Nitrotec Process in Vehicle Weight Reduction
Authors: Dawes C
Published: February 2007

Nitrotec is characterized as a low-distortion treatment for ferrous materials where surface enrichment, predominantly by nitrogen, forms a hard surface layer of epsilon iron nitride, beneath which there is a nitrogen diffusion zone. The surface layer imparts wear and corrosion resistance and the diffusion zone increases the yield and fatigue strength, particularly in thin section sizes. Process developments have significantly enhanced the corrosion resistance and aesthetic appearance of treated components to make Nitrotec competitive with electroplated finishes. Major commercialization took place during the 1980s with a wide range of successful applications from windscreen wiper systems to bumper armatures, using combinations of the unique properties obtainable from the process to provide cost and weight savings.
A Four-Phase Control Scheme of an Anti-Skid Brake System for all Road Conditions
Authors: Kuo C-Y , Yeh E C
Published: February 2007

This paper presents a new scheme of four-phase control and its design method to accommodate all road conditions for an anti-skid brake system. This control law differs from the conventional two-phase control by adding a high-pressure holding mode and a low-pressure holding mode. The elapsed time interval and the angular acceleration of the wheel are used to control the switching of these two additional modes. Firstly, a piecewise linear tyre model with two segments is used to approximate all tyre-road characteristics. Next, the threshold values for the two additional modes are determined to ensure the desired performance under all road conditions for anti-skid systems with a quick convergence rate towards the desired operating region, so that a large brake force and desirable directional stability for the vehicle can be obtained. Finally, computer simulations are performed for two selected cases with dry and wet roads, with the results showing that the desired operation is achieved in only a few cycles.
Inspection and Integrity Methodology for Storage Tanks
Authors: Kinnear D M
Published: February 2007

The integrity of large storage tanks features significantly in the budget of maintenance and inspection departments within the petroleum and petrochemical industries. The unpredicted failure of a storage tank will not only seriously affect the operating flexibility within a company, but may lead to punitive action being taken by the authorities against the company for any pollution that may occur.

A great deal of effort, as well as expense, is expended in the monitoring and inspection of storage tanks to ensure their integrity. Techniques used in predicting and assessing the condition of storage tanks are improving steadily and this paper provides an insight into techniques that are currently being used and methods that are being developed. The paper also proposes areas of research which need to be undertaken if economies are to be realized in this expensive process.
Structural Effects of Foundation Tilt on Storage Tanks
Authors: Palmer S C
Published: February 2007

Vertical cylindrical tanks for bulk storage of oil and liquefied gas are sometimes constructed on soils that are susceptible to settlement. The types of foundation settlement and their structural effects on the tank are reviewed. An arbitrary operational limit of 1 in 200 is sometimes quoted for the foundation tilt of atmospheric storage tanks. This limit is based on aesthetic considerations and on the effects on pipework connections and other attachments. Many tanks reach this limit before the end of their design life, and tank owners face difficulties in assessing the effects of foundation tilt since the current design and inspection codes give no guidance.

The purpose of this paper is to present a simple method for calculating the overturning moment, shear force and associated stresses caused by tilt of a tank, and to present a rational design basis. The procedures can be used in the design of new tanks to withstand a specified magnitude of foundation tilt and also to predict the maximum allowable tilt for existing tanks. Similarities with the overturning effects caused by wind and seismic loading are identified. The possibilities of axial buckling and shear buckling are investigated, and allowable stresses are discussed. For anchored tanks, the effects of tilt on the shell hold-down anchors are shown to be significant, and for unanchored tanks the possibility of shell uplift is discussed. A diagrammatic representation of the results is presented which allows stresses caused by tilt to be compared with stresses caused by other tank loads and the prediction of stresses caused by future tilt.

Experimental tests on a model open-top tank are reported, and indicate that tilt did not cause significant distortion of the tank.
An Investigation of Short Pitch Wheel and Rail Corrugations on the Vancouver Mass Transit System
Authors: Kalousek J , Johnson K L
Published: February 2007

Shortly after opening, the Vancouver mass transit system experienced severe rail and wheel corrugation problems. Poor alignment of wheelsets in trucks, generation of ‘roll-slip’ oscillations between wheel and rail and the development of close conformity between the wheel tread and the rail were judged to be associated with the development of corrugations. Remedies included reducing the tolerance on wheelset misalignment to ±10 minutes of arc, applying a friction modifier to wheels to change the friction characteristic between wheel tread and rail from negative to positive, regauging the track and grinding the rail to different profiles in each of the four equal sections of tangent track. These remedies have virtually eliminated corrugation from the system.
Addressing the Challenge of Aircraft Component Design and Manufacture from Metal Matrix Composites
Authors: Charles D
Published: February 2007

Metal matrix composites (MMCs) offer considerable potential for providing lightweight components exhibiting high strength, high stiffness, good wear resistance and improved elevated temperature performance in comparison to the matrix alloy. Consequently they are applicable to a wide range of aerospace products. The potential offered by this class of materials has resulted in considerable effort being expanded to address the challenges posed by the design*** and manufacture of aerospace components from these materials. These efforts have culminated in the successful design, manufacture and test of representative aircraft components from metal matrix composites.
Integrated Flying Helmets
Authors: Jarrett D N , Karavis A
Published: February 2007

The addition of vision enhancement, display and control functions to aviator's headgear is operationally attractive. Fast jets and helicopters currently under development call for headgear with a combination of these novel facilities.

This paper reviews the recent history of such helmet systems, which demonstrate admirably the inventiveness of the design teams. However, there are attendant perceptual and operational concerns and the addition of extra components invariably compromises basic ergonomic qualities.

It is suggested that a new design philosophy, which emphasizes functional integration rather than the incorporation of compatible sub-systems, has become essential. This will be assisted significantly when key optical and electro-optical technologies become mature.
The Application of Value Analysis to some Ariane 5 Launcher Sub-Systems
Authors: Broderick R W
Published: February 2007

Devtec, an aerospace engineering subsidiary of Aer Lingus, designed and developed (for manufacture in Ireland) the Vulcain engine supports for the Ariane 5 European launcher, in conjunction with SEP France. This paper describes how value analysis was applied to achieve significant cost and mass reductions. The methodology described is applicable to other aerospace projects.
The use of Math-Dynamic Models to Aid the Development of Integrated Health and Usage Monitoring Systems
Authors: Azzam H , Andrew M J
Published: February 2007

Development of integrated health and usage monitoring systems (IHUMS) involved the use of personal computer-based math-dynamic models, which in this particular case simulate a range of helicopter rotor system faults and potentially catastrophic failures. Using both theoretical and in-field data, over 120 fault cases have been analysed to identify discriminatory characteristics. This paper reports on the background of the math-dynamic models and the findings of the diagnostic analysis.
Potential Aerospace Applications for Metal Matrix Composites
Authors: Charles D
Published: February 2007

Metal matrix composites (MMCs) are of considerable interest to the aerospace industry because of their great potential for the production of lightweight, structurally efficient aerospace components. This potential has been recognized on an international level throughout the Western world, with many nations classing MMCs as being of strategic importance. This article assesses the aerospace market for MMCs and highlights the increasing efforts to exploit the potential of these materials in all sectors of the aerospace industry.
Transcutaneous Gas Tensions in the Sacrum during the Acute Phase of Spinal Cord Injury
Authors: Bogie K M , Nuseibeh I , Bader D L
Published: February 2007

The first few months following injury to the spinal cord requires constant care of the subject if tissue breakdown is to be avoided. The management of acute traumatic cases involves complete bedrest in a supine position with appropriately positioned pillows to minimize trauma to the bone prominences. This study assesses the effectiveness of the management procedure in terms of the tissue response at the sacrum of 15 acute spinal cord injured subjects, The measurement of mean interface pressures during a representative period of recumbancy was performed and these were related to changes in transcutaneous gas tensions (TcPO2 and TcPCO2), which are reliable indices of tissue viability. A series of six variables was established which were compared to each other using non-parametric statistical analyses. It was shown that this group of subjects demonstrated a normal mechanism whereby the level of carbon dioxide was able to control the local vascular tone. The results also suggested that the practice of gapping at the sacrum should be revised to reduce mean sacral pressures and minimize the possibility of tissue breakdown, the risk of which is constant throughout the first three months following injury.
The Function of Bipolar Hip Prostheses—A Laboratory Study Using Cadaveric Acetabula
Authors: Wetherell R G , Unsworth A , Amis A A
Published: February 2007

Cadaveric acetabula were mounted in a hip simulator and the friction developed in each during articulation with a series of metal femoral head prostheses of differing sizes was measured. In a separate study, assembled Hastings bipolar hip prostheses were subjected to weight-bearing forces in the same acetabula and their self-righting mechanism was observed.

The self-righting mechanism was found to function efficiently, in most cases overcoming the combined friction of the inner and outer articulations of the Hastings hip. However, during motion in the hip simulator a wide variation of friction was observed between different acetabula and within the same acetabulum with differing head size. In several cases this acetabular friction was found to be less than the friction in the inner articulation of the Hastings bipolar hip prosthesis, and this may explain some cases of reported failure of biarticular function.
The CADCAM Contribution to Customized Orthopaedic Implants
Authors: Crawford H V , Unwin P S , Walker P S
Published: February 2007

CADCAM (computer aided design/manufacture) production methods are often associated with mass production; working in the medical field at the Department of Biomedical Engineering, the requirement is for one-off, individualized implants.

Using a knowledge-based system, implant designs are produced from X-ray data. Assembly from modular components has greatly reduced the production time of implants for bone tumour cases.

CADCAM techniques are also used in the production of custom-made hip replacements using digitized data gathered from radiographs. Femoral canal shape is calculated and the optimal implant designed and manufactured from titanium alloy on the Department's CNC (computer numerically controlled) machines.
Engineering Design of Vascular Prostheses
Authors: How T V , Guidoin R , Young S K
Published: February 2007

The replacement and bypass of arteries of diameter greater than 6 mm with textile vascular prostheses has proved very successful since they were first introduced forty years ago. Although manufacturers continue to improve their products and make them of consistent quality for increased safety and performance and to facilitate their use by surgeons, most of the research work in this area is concerned with the development of small-diameter prostheses. Current expanded PTFE and textile prostheses do not perform satisfactorily when their diameters are reduced to less than 6 mm. For the small-diameter prostheses it will be necessary to develop less thrombogenic materials and to design the structure of the prostheses more closely to match the mechanical properties of the natural arteries. The purpose of this paper is to discuss the design requirements and to review the development of large- and small-diameter vascular prostheses.
Liver Blood Flow: Non-Invasive Estimation Using a Gamma Camera
Authors: Tindale W B , Barber D C , Smart H L , Triger D R
Published: February 2007

A non-invasive radioisotope technique for the measurement of total liver blood flow (TBF) is described. The method requires the use of two intravenously administered tracers, 99mTc (technetium 99m) human serum albumin (HSA) and 99mTc colloid. Computer analysis of first-pass time activity curves for HSA for liver and lung tissues yields values for the arterial and portal contributions to liver blood flow, from which TBF can be determined. These values are then corrected for attenuation using the images of the colloid distribution. The use of the method is illustrated in 17 subjects. Assumptions, limitations and possible applications of the technique are discussed.
Venous Haemodynamics—A Consideration of Macro- and Microvascular Effects
Authors: Mani R
Published: February 2007

In health, valves in the deep veins function unidirectionally permitting blood flow towards the heart. This function is often degraded following deep vein thrombosis leading to venous hypertension and disturbed haemodynamics in the legs of the patient. Hypertension, in turn, promotes venous ulceration through a series of degenerative pathological steps. Traditional methods of treatment include leg elevation and compression using elasticated garments or bandaging. These techniques manage the problem with varying success but do not cure it. Recent advances in surgical research suggest that novel techniques are being developed for treating valve incompetence. In these circumstances, vascular scientists should be examining methods of addressing both the macro- and the microcirculation so that changes in these consequent to venous hypertension may be measured. This review examines existing methods of measuring the macrocirculation as well as the potential techniques to study effects of venous haemodynamics in the microcirculation.
A Model of Human Knee Ligaments in the Sagittal Plane: Part 2: Fibre Recruitment under Load
Authors: Zavatsky A B , O'Connor J J
Published: February 2007

A mathematical model of the knee ligaments in the sagittal plane is used to study the forces in the cruciate and collateral ligaments produced by anterior/posterior tibial translation. The model is based on ligament fibre functional architecture. Geometric analysis of the deformed configurations of the model ligaments provides the additional compatibility conditions necessary for calculation of the statically indeterminate distributions of strain and stress within the ligaments and the sharing of load between ligaments. The investigation quantifies the process of ligament fibre recruitment, which occurs when fibres made slack by passive flexion/extension of the knee stretch and change their spatial positions in order to resist applied loads. The calculated ligament forces are in reasonable agreement with experimental results reported in the literature. The model explains some subtleties of ligament function not incorporated in models that represent the ligaments by a small number of lines.
A Device for Wear Resistance Tests of Artificial Heart Valves
Authors: Gorshkov Y V , Evdokimov S V , Kombalov V S
Published: February 2007

According to the International Standard ISO 5840: 1990 the wear resistance test is a necessary step in the development and production of artificial heart valves (AHV). In developing the device, it is important that a reliable prediction is made of AHV longevity, as a number of specific problems appear that are connected with the results of tests, duration of testing, efficiency and reliability of the testing device.

In this paper a procedure is outlined of service life testing of mechanical AHV and a description of the device is given. A comparative example of loads acting on AHV, operating in the accelerated wear testing device and in the pulse duplicator of the physiological mode is also described.
A Full Numerical Solution to the Problem of Microelastohydrodynamic Lubrication of a Stationary Compliant Wavy Layered Surface Firmly Bonded to a Rigid Substrate with Particular Reference to Human Synovial Joints
Authors: Dowson D , Jin Z M
Published: February 2007

A full numerical solution procedure has been developed for the microelastohydrodynamic lubrication analysis of a stationary compliant wavy layered surface firmly bonded to a rigid substrate. The results obtained have been compared with those using a simplified method adopted by Dowson and Jin (I) and good agreement has been obtained.
An Approach to Determining the Kinematic Parameters of Biomechanical Systems with Applications to the Wrist
Authors: Pittman P , Colbaugh R , Glass K , Rowen B
Published: February 2007

This paper presents an accurate and robust approach for determining the kinematic parameters of biomechanical systems. A computationally efficient algorithm is given for estimating the translation vector and rotation matrix of a moving body from measurements of the position of at least four spatially distributed points on the body. This algorithm provides an estimation of the spatial location and orientation of the body which is less sensitive to measurement error than other methods. It is indicated how the kinematic parameters can be used to determine the linear translation and angular rotation of the moving body in terms of an anatomically relevant coordinate system. The design, fabrication and calibration of an inexpensive, serial-link, three-dimensional mechanical digitizer for use in data acquisition is described. This device is kinematically optimized and is easy to use for accurate data collection. An implementation of this approach to quantifying certain aspects of the kinematics of the human wrist is discussed.