bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the Dynamics of Coal and Mineral Cutting
Authors: Edwards J. B. 
Published: October 2007

A dynamic model is developed for coal and mineral cutting machines which exhibits all their important behavioural characteristics. In particular, the model produces the characteristic hopping motion observed in practice to take place at frequencies closely related to the speed of rotation of the cutting head. The low-frequency instability of simple, integral load-control systems is also verified by simulation. Frequency-response analysis is shown to predict the practically observed and simulated system behaviour. the analysis necessitating a describing-function approach to the modelling of stick/slip effects in the machine haulage system, which are shown to exercise an important control on the limit-cycling of the regenerative cutting dynamics. The analysis is shown to be applicable to systems using both conventional haulage (feed) systems of low stiffness, and also to stiff transmission systems.
Leadership by Engineers
Authors: Garnett John 
Published: October 2007

To survive, society depends, amongst other things, on the successful implementation of the ideas of engineers. To implement his design or conceptual thought, the engineer relies increasingly on the co-operation of large numbers of people: other engineers, draughtsmen, fitters, supervisors and men and women in design, construction, production and maintenance. This lecture suggests that the benefits of engineering will come to our society only if engineers give more attention to achieving the commitment of the gifts of other people in making things happen. An outline is given of some common sense leadership actions which engineers must take during the last twenty years of the twentieth century if our society is to advance.
Orifice Restrictor Losses in Journal Bearings
Authors: Pink E. G. , Stout K. J. 
Published: October 2007

Details of a study concerning orifice restrictor losses in externally pressurized gas lubricated journal bearings are given. The type of compensation considered is the pocketed orifice design. The analysis presented includes the effects of pressure recovery in the pocket and entrance loss effects at inlet to the bearing film. Also, by treating the flow in the bearing film local to the pocket as radial flow, the effect of dispersion is accounted for. It is shown that good agreement exists between computed and experimental results in pressure profiles and also for load capacity up to touch-down conditions. From the analysis, the effect of the inherent compensation factor, number of orifices and pocket diameter on load capacity is discussed.
A New Technique for Estimating System Uncertainty in Design
Authors: Blockley D. I. , Ellison E. G. 
Published: October 2007

Components operating in modern power plant, such as nuclear reactors, gas and steam turbines are subject to complex loading cycles at elevated temperatures so that combined creep/fatigue damage often occurs. Estimates of the life of these components are difficult because of the indefinite nature of the assumed constitutive model and also of the relevant material properties. In an attempt to handle this problem, a new predictive technique is presented which is based on the concept of ‘fuzzy sets’ (1). The basic ideas behind fuzzy sets are simply explained and then applied to test results previously obtained (2) on a 1 Cr Mo V steel. A simple linear cumulative damage rule is used for illustration. Using the method, estimates of system uncertainty can be made which can then be combined with random uncertainty of the parameters to obtain a probability measure of the number of loading cycles to failure of a component. Cumulative distribution functions for the system uncertainty in the test results are produced and their usefulness to the designer discussed.
Engine Design Experiences and Development of Critical Components
Authors: Robinson J. E. 
Published: October 2007

The paper provides a review of a number of engines for which the author had some personal design and/or development involvement and responsibility. Details are given of methods of construction and technical performance which illustrate progress in engine design over the last forty years, and the contribution made in development by engine component specialists. Predictive techniques and uses of specialized rig tests used in piston assembly development are described, which reduce development costs and time, and improve engine reliability. Quality control techniques are briefly compared and the need is shown for a greater degree of ‘in-process’ control, to be developed in the next decade, to obtain improved quality levels with no concurrent cost increase. It is suggested that the main prime movers in use during the first two decades of the next century will still be recognizable as reciprocating engines, but that efficiencies will be improved by reduced friction and by a more efficient response to engine load demand. It is believed that in the search to conserve the world's fuel resources, and in the increasing demand for improvements in the ecology and consumer protection, there will be an increasing demand—and recognition—for the dedicated engineer.
Development Work on Steam Vent Pipe Silencing
Authors: Clayton J. K. , Cramer S. H. 
Published: October 2007

The paper describes the practical steps taken in the development of a light-weight steam discharge silencer, mounted at the outlet of the vent pipe. With various degrees of valve throttling of superheater start-up valves as well as safety valves, the sound pressure level (SPL) effects at the vent pipe outlet were analysed before and after silencing. Various configurations of the silencer were tested on steam discharge, some resulted in increased attenuation. Throughout the development programme, steam flow rates were measured along with SPL.
Improvement in the Torque Characteristic of a Two-Stroke Opposed Piston Diesel Engine
Authors: Blencoe W. R. , Few P. C. , Picken D. J. 
Published: October 2007

This paper gives details of an investigation into the improvement of the torque characteristics of a turbocharged Commer TS3 two-stroke diesel engine. At low engine speeds when there is a need for a rising torque characteristic the desirability of using a combustion chamber before the turbine is investigated: (a) theoretically using a computer matching program, and, (b) experimentally by removal of the scavenge blower and incorporating a combustion chamber in the exhaust ducting. Theoretical and experimental work is reported in this paper.
Water Hammer Phenomena in Thermal Power Station Feed Water Systems
Authors: Wilkinson D. H. , Dartnell L. M. 
Published: October 2007

The phenomenon of water hammer in stagnant hot fluid systems has been manifested by the fracture of a number of cast iron valves and other components in power station low pressure feed water systems and other similar systems. A comprehensive investigation proved necessary into all aspects of this phenomenon. The investigation involved a survey of water hammer events, experimental work, data acquisition, pressure testing, calculation of forces and the determination of the strength of individual components. From this work has sprung a clear understanding of the sequence of events occurring when pressure is reduced on hot feed water and flash steam is produced which subsequently escapes or condenses and fluid columns recombine at speed and produce pressure pulses. Experimental and theoretical work has revealed the magnitude of such pressure pulses and also revealed that steel pressure parts will not fail when subjected to the forces arising from thermodynamically induced water hammer, because steel pipes limit transient hydraulic pressures by dilating and steel valves are sufficiently strong. The dynamic response of complex pipework system to stimulation by water hammer events requires further investigation, but practical experience indicates that failure of steel system components is unlikely from dynamic movements, although damage may be suffered by pipe hangers, seismic restraints etc.
The Flow Characteristics of a Piston-Cylinder Assembly with an Off-Centre, Open Port
Authors: Morse A. P. , Whitelaw J. H. , Yianneskis M. 
Published: October 2007

Laser-Doppler anemometry has been used to measure the mean and r.m.s. values of the velocity components of the flow in a reciprocating assembly containing an off-centre, open port in the cylinder head and a flat piston. The port was inclined at an angle of 60° to the head and gave rise to a three-dimensional flow with no significant compression. The rotational speed was 200 rev/min, ensuring fully turbulent flow. The measurements were restricted to the axial and circumferential velocity components and were made on three radial planes in order to describe the flow in sufficient detail. The results are presented in the form of radial profiles and vector diagrams in both the axial and cross-stream planes. The main flow pattern on the intake stroke is of the same general shape as that previously obtained with a symmetric port, a large vortex occupying the space bounded by the indrawn jet with a much smaller vortex in the corner between the cylinder head and wall. These vortices are however no longer symmetrical about the cylinder axis, but vary in both size and intensity with circumferential position. In the cross-stream plane, the primary vortex is characterized by the presence of a stress-induced swirling motion on either side of the plane of symmetry with velocities significantly greater than the circumferential velocity of the jet. At mid-stroke, these vortices rotate counter to the jet, but at 144° ATDC, the direction of rotation reverses over part of the length of the vortex and is in the same sense as the jet motion. On the exhaust stroke, the flow patterns are relatively simple with quasi-parallel axial flow and little swirl until the port is approached, when the outgoing jet accelerates and begins to rotate in a direction opposite to its motion on the intake stroke.
Effects of Flow and Geometry Boundary Conditions on Fluid Motion in a Motored IC Model Engine
Authors: Arcoumanis C , Bicen A F , Vlachos N S , Whitelaw J H 
Published: October 2007

Measurements of ensemble-averaged axial velocities and the r.m.s. of the corresponding fluctuations, obtained by laser-Doppler anemometry, are reported for axisymmetric flow in a non-compressing piston-cylinder assembly motored at 200 rev/min simulating an IC engine. The inlet geometry comprised an open valve, located centrally and flush with the cylinder head, with seat angles of 30° and 60° and incorporating 30° swirl vanes. Results are presented for bore-to-stroke ratios of 0.83 and 1.25 and swept-to-clearance volume ratios of 2,3 and 9. The results indicate strong similarities between the flow structures for different stroke and clearance; a system of vortices is formed with a large vortex occupying most of the flow space and with smaller vortices in the corners between the wall, piston and cylinder head. The influence of valve seat angle is more pronounced and results, for the 30° angle, in adherence of the incoming jet to the cylinder head with increase of the overall turbulence levels and creation of stronger and longer living vortices. Previous results obtained in related compressing and non-compressing flow configurations are reviewed and, together with the present results, enable the influence of a wide range of possible geometric and flow boundary conditions to be quantified.
Powder Compaction: Fundamentals and Recent Developments
Authors: Fischmeister Hellmut F 
Published: October 2007

The lecture reviews processes and mechanisms of powder compaction in dies, by cold or hot isostatic pressing, and by various other methods. The review will also include the hot and cold forging of powder preforms. Key problems of the main processes will be discussed, such as mass flow in the powder bed during compaction, which is required to achieve homogeneous density distribution in a part, or the role of powder lubrication. Applications of powder compaction are described using examples from such areas as the manufacture of sintered machine parts, high-strength automotive parts made by powder forging, the fabrication of mill shapes from powder (e.g., high speed steel or stainless steel tubing), and the production of aircraft engine parts by hot isostatic pressing.
The Effect of Joint Flexibility on the Torsion of a Vehicle Body
Authors: Sharman P W 
Published: October 2007

Experiments on thin fabricated box members in a tee joint configuration revealed deformations which could not be correlated with beam-type models, even when spring elements were introduced at the joint. The behaviour was also observed in finite element analyses of the joints. Part of the cab structure of a heavy goods vehicle which formed a plane frame with fabricated members of closed cross-section was tested in torsion and the stiffness compared with theoretical predictions. The application of classical beam and torsional theory gave a result which was approximately ten times the experimental value. A further theoretical estimate, which included the joint flexibility as predicted by a finite element model of the localized region at the joint, gave an improved result which was 26 per cent higher than the experimental value.
The Modelling of Semiflexible Conveyor Structures for Coal-Face Steering Investigations: Part 1: Spatially Discrete Models
Authors: Edwards J B , Yazdi A M S R , Wolfenden J R 
Published: October 2007

Discrete dynamic programming is used for the development of a computer simulation of armoured semiflexible conveyor (AFC) structures used in modern longwall coal mining. The object of the simulation is the investigation of the vertical steering characteristics of face installations, the potential long-term instability of which is a continuing problem underground. The way in which the AFC structure moulds itself to the undulating floor cut by the coal winning machine (the power-loader) between successive cuts is a crucial factor in the steering behaviour of the entire face system. This, the first of two companion papers, treats the AFC as a chain of loosely coupled piecewise rigid segments (trays) resting on a solid coal floor. Such a model is found not to greatly assist the stability of the multipass longwall process. An elastic model is examined in the companion paper.
Training Without the State? New Labour and labour markets
Authors: King Desmond , Wickham-Jones Mark 
Published: October 2007

English
In 1996 the British Labour Party abandoned its commitment to a state-led training policy funded through a levy on business. It adopted a new scheme based on individual plans with minimal public intervention and no levy. Drawing on archival sources, this article examines the development of Labour’s policy towards training over the last 15 years. The authors argue that the new proposals mark the failure of the Party’s attempt to locate itself within the mainstream of European social democracy. Three factors explain this outcome: the changing nature of Labour’s relationship with trade unions; an acceptance by the Party of the UK’s uncoordinated market economy; and the decision by Labour to advance an electoral strategy aimed at reassuring business and voters. The Party’s effort to meet employers’ training policy preferences has decisively shaped the nature of its social democratic commitments.
Devolution and Economic Development in France
Authors: Rogers Vaughan 
Published: October 2007

English
The role of the French regions in economic intervention since the decentralisation reforms of the 1980s has been considerably more significant than recent appraisals have suggested. The diversity in the strategies adopted from one region to another indicates an increased capacity to shape policy initiatives according to their own priorities. The enhancement of regional autonomy is examined in the case of Brittany, where the development of an original pattern of local authority relations in the sphere of economic intervention has helped to overcome some of the obstacles to the effective functioning of the system instituted by the decentralisation programme.
Factors affecting wettability and bond strength of solder joint couples
Authors: Sobczak Natalia , Kudyba Artur , Nowak Rafal , Radziwill Waldemar , Pietrzak Krystyna 
Published: October 2007

AbstractThe paper discusses the scientific understanding of the role of interfacial phenomena in joining of dissimilar materials using liquid-phase-assisted processes. From the example of the Sn-alloy/Cu system, it is demonstrated that interaction in the liquid solder/substrate couples is accompanied by a number of complex interfacial reactions leading to significant changes in the structure and chemistry of interfaces (solder/substrate, solder/environment, substrate/environment) and remaining solder layer that finally influence the mechanical properties of solder joints. The experimental data on wetting behavior, interface characterization, and mechanical properties of different solder/metal substrate couples are analyzed in order to display the role of such factors as time and temperature of interaction, environment (protective atmosphere, flux), presence of oxide films on interfaces, alloying additions to a solder, formation of interfacial phases, and porosity.
Osteoblast-Targeted Expression of Sfrp4 in Mice Results in Low Bone Mass
Authors: Nakanishi Rika , Akiyama Haruhiko , Kimura Hiroaki , Otsuki Bungo , Shimizu Motoyuki , Tsuboyama Tadao , Nakamura Takashi 
Published: October 2007

Abstract
Transgenic mice overexpressing Sfrp4 in osteoblasts were established. These mice exhibited low bone mass caused by a decrease in bone formation.
Introduction: We recently reported that single nucleotide polymorphisms in the secreted frizzled-related protein 4 (Sfrp4) gene are responsible for low peak BMD in senescence-accelerated mouse (SAM) P6. In vitro studies revealed inhibition of osteoblast proliferation by Sfrp4, which is supposed to be mediated by canonical Wnt signaling.
Materials and Methods: We examined the expression of Sfrp4 in neonate long bones by in situ hybridization and generated transgenic mice in which Sfrp4 was specifically overexpressed in osteoblasts under the control of a 2.3-kb Col1a1 osteoblast-specific promoter. Next, we compared the phenotype of Sfrp4 transgenic (Sfrp4 TG) mice with that of mice in which one allele of β-catenin was conditionally disrupted in osteoblasts (βChet), and administered lithium chloride (LiCl) to Sfrp4 TG mice.
Results: Hemizygous Sfrp4 TG mice exhibited a 30% reduction of trabecular bone mass compared with that in wildtype littermates at 8 wk of age, and histomorphometrical analysis showed decreases in both osteoblast numbers and bone formation rate. βChet mice exhibited a 17% reduction of trabecular bone mass in distal femora caused by an increase in the osteoclast number and a decrease in bone formation rate. Furthermore, LiCl administration rescued the bone phenotype of Sfrp4 TG mice.
Conclusions: Expression of Sfrp4 in periosteum and bone tissues suggested the role of Sfrp4 in osteoblasts, and we identified that overexpression of Sfrp4 in osteoblasts suppressed osteoblast proliferation, resulting in a decrease in bone formation in vivo. Partial suppression of β-catenin/canonical Wnt signaling also impaired bone formation, and activation of the signaling restored low bone mass of Sfrp4 TG mice. Thus, these results indicate that Sfrp4 decreases bone formation at least in part by attenuating canonical Wnt signaling in vivo.
Complete Volumetric Decomposition of Individual Trabecular Plates and Rods and Its Morphological Correlations With Anisotropic Elastic Moduli in Human Trabecular Bone
Authors: Liu X Sherry , Sajda Paul , Saha Punam K , Wehrli Felix W , Bevill Grant , Keaveny Tony M , Guo X Edward 
Published: October 2007

Abstract
Trabecular plates and rods are important microarchitectural features in determining mechanical properties of trabecular bone. A complete volumetric decomposition of individual trabecular plates and rods was used to assess the orientation and morphology of 71 human trabecular bone samples. The ITS-based morphological analyses better characterize microarchitecture and help predict anisotropic mechanical properties of trabecular bone.
Introduction: Standard morphological analyses of trabecular architecture lack explicit segmentations of individual trabecular plates and rods. In this study, a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Contributions of trabecular type-associated morphological parameters to the anisotropic elastic moduli of trabecular bone were studied.
Materials and Methods: Seventy-one human trabecular bone samples from the femoral neck (FN), tibia, and vertebral body (VB) were imaged using μCT or serial milling. Complete volumetric decomposition was applied to segment trabecular bone microstructure into individual plates and rods. The orientation of each individual trabecula was determined, and the axial bone volume fractions (aBV/TV), axially aligned bone volume fraction along each orthotropic axis, were correlated with the elastic moduli. The microstructural type-associated morphological parameters were derived and compared with standard morphological parameters. Their contributions to the anisotropic elastic moduli, calculated by finite element analysis (FEA), were evaluated and compared.
Results: The distribution of trabecular orientation suggested that longitudinal plates and transverse rods dominate at all three anatomic sites. aBV/TV along each axis, in general, showed a better correlation with the axial elastic modulus (r2 = 0.95∼0.99) compared with BV/TV (r2 = 0.93∼0.94). The plate-associated morphological parameters generally showed higher correlations with the corresponding standard morphological parameters than the rod-associated parameters. Multiple linear regression models of six elastic moduli with individual trabeculae segmentation (ITS)-based morphological parameters (adjusted r2 = 0.95∼0.98) performed equally well as those with standard morphological parameters (adjusted r2 = 0.94∼0.97) but revealed specific contributions from individual trabecular plates or rods.
Conclusions: The ITS-based morphological analyses provide a better characterization of the morphology and trabecular orientation of trabecular bone. The axial loading of trabecular bone is mainly sustained by the axially aligned trabecular bone volume. Results suggest that trabecular plates dominate the overall elastic properties of trabecular bone.