bluuebunny/crossref_metadata_2025 huggingface dataset:
Interferometric Study of the Temperature Field Created by a Quasi-Plane Cold Air Jet and an Adjacent Flat Plate
Authors: Hammond G. P. , Fung W. S. , O'Callaghan P. W. , Probert S. D.
Published: February 2007

The Chilowsky effect, whereby a jet initially inclined to a flat plate subsequently becomes attached to it, thereby forming an enclosed region of recirculation, has been studied. A quasi-plane cold air jet (at about 0°C) issued parallel or inclined to an adjacent adiabatic flat plate, with a slot-exit Reynolds number <5 times 103, into quiescent ambient air (at about 16°C). The temperature field in and around the jet was mapped using a 15-cm field-of-view Mach-Zehnder interferometer for a downstream distance of 90 slot widths and compared with predictions from Glauert/Seban-Back theoretical model for turbulent wall jets.

Transverse velocity and temperature profiles downstream of the attachment point were found to be near-similar for inclination angles up to 40°. The attaching inclined jets exhibited two wall-temperature decay rates, similar to those observed for three-dimensional wall jets. To utilize the Chilowsky phenomenon, continuous linear air-conditioning diffusers need to be designed with exit angles of less than 50°, thereby ensuring jet attachment to the ceiling and so avoiding discomfort to human occupants.
Microtopographic Influence of Nominally Flat Metallic Surfaces upon Their Thermally Reflective Behaviour
Authors: O'Callaghan P. W. , Probert S. D.
Published: February 2007

The total reflectivity as well as the spatial distribution of the reflected energy is influenced by the topography of the reflecting surface. It has been commonly, but mistakenly, assumed that the angular variation of thermal radiation reflected from real surfaces has a directional distribution that falls between the diffuse and specular limits. For roughened surfaces, maxima in the reflected, total, radiant-intensity vector distribution occur at viewing directions other than at the angle of specular reflection, even when the mean optical roughness (i.e. r.m.s. roughness divided by wavelength of the incident radiation) is less than unity. Off-specular phenomena occur if the product of the mean normalized absolute surface slope and the predominant radiation wavelength is smaller than about 12. The magnitude of the off-specular angle is then a function of the mean surface slope, the r.m.s. roughness, the predominant wavelength of the incident radiation and its angle of incidence.
Numerical Solution for the Spherical Bubble Growth Problem in a Uniformly Ultraheated Liquid
Authors: Saitoh T. , Shima A.
Published: February 2007

A multi-point, implicit-type, finite-difference method for solving the bubble growth (or collapse) problem in an ultraheated liquid is proposed. The method is applicable to both inertia-controlled growth and heat-diffusion-controlled growth. The results are compared with several asymptotic solutions, involving Plesset-Zwick and Mikic-Rohsenow-Griffith solutions. Present results strongly support the Mikic-Rohsenow-Griffith solution for the wide range of bubble growth conditions, e.g. given fluids, pressure, liquid ultraheat, etc.
Research Note: Two-Phase Flow through Sharp-Edged Orifices
Authors: Chisholm D.
Published: February 2007

Equations are developed for the pressure drop over sharp-edged orifices during the flow of incompressible two-phase mixtures. The velocity ratio is assumed constant during flow through the orifice, and on this basis analysis of the data leads to the following equations for the velocity ratio: for X ≥ 1, K = ( pL/pHOM)1/2 for X ≤ 1, K = ( pL/ pG)1/4.
Pressure-Distribution Measurements in Rotary Forging
Authors: Hawkyard J. B. , Gurnani C. K. S. , Johnson W.
Published: February 2007

Experiments on the rotary forging of discs are described in which measurements are taken of pressure distribution under the rocking die using a pressure-sensing platen.

The results suggest a deformation mechanism for the spread of the disc, involving the development of plastic hinges away from the immediate die contact area. This would explain central tensile failures and related phenomena observed previously.
The Significance of the Isotropic Hardening Rule in Relation to the Stress-Strain Curves of a Pre-Strained Metal
Authors: Daneshi G. H.
Published: February 2007

Defining yield in different ways leads to different shapes of yield surface. This is shown in connection with tests on commercially pure aluminium. Attention is drawn to a flow surface associated with the isotropic hardening rule. Experimental results suggest that, beyond this surface, the stress-strain curves of a pre-deformed specimen are parallel to similar curves for an annealed metal.
Analysis of Electroforming with Direct Current
Authors: McGeough J. A. , Rasmussen H.
Published: February 2007

The process of electroforming with direct current is analysed by a perturbation method for a case in which the amplitude and slope of the electroformed metal layer are small compared with the inter-electrode gap width. Conditions are established for which the metal layer has a uniform thickness. The converse problem of electroforming a metal layer, whose lower face is irregular but whose upper face is effectively flat, is also investigated.
Thermal Resistances of Stacks of Thin Layers under Compression
Authors: Al-Astrabadi F. R. , Probert S. D. , O'Callaghan P. W. , Jones A. M.
Published: February 2007

Stacks, each comprising a number of thin, ‘flat’ layers of tin-coated steel, were compressed in a direction normal to the individual layers under loadings of up to 8 times 106Nm-2. Two distinct modes of deformation occurred: a layer-flattening region at low loads ( P/M < 10-3), and a surface-waviness deformation region under higher loading pressures. The thermal resistance per unit area per unit length of each stack (in a vacuum of better than 7 times 10-2Nm-2) was inversely proportional to the compression per layer for freshly-assembled stacks throughout the loading region corresponding to macroscopic conformity. Hystereses in the thermal resistance and compression characteristics were observed during the initial loading/unloading cycles. A dimensionless correlation relating conductance to applied loading is proposed for stacks of bedded-down thin layers.
Research Note: The Downstream Influence of Inertia on Simple Gas Bearing Element Performance
Authors: Tully N.
Published: February 2007

In laminar flow between flat plates for parallel, radial inward, and in some circumstances radial outward flow, the flow velocity increases as the density falls. If the bearing is long enough, and the ambient pressure low enough, the film will ‘choke’, i.e. the pressure gradient at exit becomes infinite. An increase in the pressure at entry to the film then results in an exit plane pressure greater than ambient. The conditions for the above flows to choke are examined, and the effect on the performance of a simple, orifice-compensated, parallel-flow bearing element is described. It is found that load capacity is enhanced, but optimum stiffness reduced, when compared with an inertialess flow prediction.
Fluid Particle Trajectories in Stirling-Cycle Machines
Authors: Organ A. J.
Published: February 2007

Equations are set up by means of which arbitrarily selected particles of working fluid may be ‘tracked’ continuously throughout a cycle. Pressure is assumed to be instantaneously uniform, but account is taken of variable working space temperatures. Fluid particle trajectory maps are presented for machines of two types. One has opposed pistons following the ‘ideal’, discontinuous motion. The other has coaxial piston and displacer actuated by the rhombic drive mechanism. For the limiting case of isothermal phases, pressure is plotted against specific volume, and temperature against specific entropy for selected tracked particles. Thus it is deduced that, even when the unswept volume is taken to be zero, and piston motion to be discontinuous, it is not possible to draw either a unique p-v diagram or a unique t-s diagram for any practical embodiment of the Stirling cycle. It is demonstrated that such relationships may be viewed instead as summations of an infinity of p-vs or t-s relationships, that is, one for each discrete working fluid element.
Negative Pressures under a Lubricated Piston Ring
Authors: Brown S. R. , Hamilton G. M.
Published: February 2007

Large negative pressures have been observed in the oil film lubricating a piston ring. Just after the dead-centre position, these reach a peak value of −0.78 MN/m2 (-113.1 lbf/in2), which is far in excess of the values normally assumed to be needed to produce cavitation. They are only sustained for a short period of time, but have the important effect of reducing the minimum film thickness.
The Dynamics of a Hooke's Joint Gyroscope with Non-Orthogonal Flexure Axes
Authors: Fox C. H. J. , Burdess J. S.
Published: February 2007

The dynamical characteristics of a Hooke's joint gyroscope with non-orthogonal flexure axes are described. The natural frequencies of the gyroscope are shown to vary with the amount of non-orthogonality present, but the tuning conditions and the conditions for the suppression of drift resulting from twice spin speed angular vibration are shown to be independent of non-orthogonality. For both the tuned and untuned cases, the response to an applied rate of turn has been assessed and errors arising from flexure axis non-orthogonality are identified.
The Measurement and Interpretation of Flow within Rotating Stall Cells in Axial Compressors
Authors: Day I. J. , Cumpsty N.A.
Published: February 2007

Detailed flow measurements obtained by a new measuring technique are presented for the flow in a stalled axial-flow compressor. Results were obtained from a wide range of compressor builds, including multi-stage and single-stage configurations of various design flow rates and degrees of reaction. Instantaneous recordings of absolute velocity, flow direction and total and static pressures have been included for both full-span and part-span stall.

With the aid of these results, it has been shown that the conventional model of the flow in a stall cell is erroneous. An alternative model is proposed, based on the observation that the fluid must cross from one side of the cell to the other in order to preserve continuity in the tangential direction. An investigation of the experimental results also reveals the finer details of the flow in the cell and shows how these details are related to the design flow rate of the compressor. The influence of these cell details on the power absorbed by a stalled compressor are investigated, and consideration is given to the complex pressure patterns encountered in the compressor.
The Complete Three-Dimensional Calculation of the Compressible Flow Field in Turbo Impellers
Authors: Krimerman Y. , Adler D.
Published: February 2007

The calculation of the complete, three-dimensional, subsonic, non-viscous flow in turbo impellers of arbitrary shape (axial, radial or mixed flow) is presented. The finite-element method is used to solve modified subsonic Wu equations. The solution is carried out using four basic algorithms: ( a) axisymmetric flow calculation in the meridional surface, ( b) flow calculation on an axisymmetric blade-to-blade surface, ( c) non-axisymmetric corrected flow calculation on a meridional surface, and ( d) flow calculation on a non-axisymmetric blade-to-blade surface. These basic algorithms are combined into a calculation procedure in which algorithms a and b are used as the first two steps, and algorithms c and d are alternately used until convergence is achieved. Algorithms b, c and d are applied to a number of stream surfaces.
An Analysis of the Yield Criteria and the Stress-Strain Relationships of a Pre-Strained Commercially Pure Aluminium
Authors: Daneshi G. H.
Published: February 2007

An analysis of the stress path and the strain trajectory of a pre-strained engineering material in the deviatoric plane is presented. The deviatoric stress vector, which for a pre-strained material is initially at an angle to the strain trajectory, is shown to coincide with it after the ‘recoverable’ energy is consumed.

Experimental work is carried out on the yield criteria and the stress—strain relationships of a pre-strained commercially pure aluminium. The significance of the isotropic hardening rule in relation to a metal's straining memory is demonstrated. It is shown that beyond a stress level associated with an isotropic hardening rule based on the Mises yield criterion, the representative stress—strain curves of a pre-strained specimen run parallel to that of an annealed material.
The Response of a Hooke's-Joint Gyroscope to Linear Vibration
Authors: Burdess J. S. , Fox C. H. J. , Maunder L.
Published: February 2007

The response of an unbalanced Hooke's-joint gyroscope to linear vibration is considered. Six major resonant frequencies are identified.

It is shown that, if the gyroscope is subjected to linear vibration either along the spin axis at the spin frequency, or perpendicular to the spin axis at twice the spin frequency, measurement errors may be generated as a result of mass unbalance. These errors are shown to depend not only upon the degree of unbalance but also upon the amplitude and phase characteristics of the vibration. Compensation by the application of suitable control torques is shown to be possible.
The Effect of Mass Flow Rate on the Reflection Behaviour of Small-Amplitude Pressure Waves from Duct Terminations
Authors: Ali M. A. , Gill K. F. , Imrie B. W.
Published: February 2007

This paper describes an investigation of the reflection characteristics of small-amplitude pressure waves in the presence of steady flow in a duct. A correlation technique employing pseudo-random binary-sequence (p.r.b.s.) pulses is introduced. A theoretical model of the process is presented together with considerations of correlation analysis. The results show agreement between the experimental results and the model; they further indicate that, in the presence of a steady flow component, there is a significant effect on the reflection behaviour of plane pressure waves for a reduction in the area terminating a duct.

The experimental technique is effective at very low flow velocities (Mach number = 0·02, Reynolds number = 30 times 103) and establishes a linear relationship between a reflection coefficient and a non-dimensional mass flow number. A reflection coefficient of flow is introduced as an appropriate parameter for such conditions.

The procedure could be applied to a wide range of industrial processes to determine flow coefficients of duct elements in situ, to optimize flow processes and to locate leakage flows.
Thin-Film Flows with Thermoelastically Deformed Boundaries
Authors: Banerjee B. N. , Burton R. A.
Published: February 2007

Equilibrium solutions are given for the thermoelastic displacements of an initially wavy, moving surface subjected to non-uniform viscous heating derived from a hydrodynamic lubricant film. The configuration studied is similar to a flexibly mounted face seal with one metallic face running against a thermal insulator. Changes in mean film-thickness with changing speed are discussed with reference to earlier analyses which predicted thermoelastic instability and to experiments which illustrated this. The operating conditions approach those where instability was predicted for conditions of fixed mean film thickness; however, no instability is predicted for present conditions where axial load is fixed. Thermoelastic effects upon growth of surface waviness become significant when the sliding speed exceeds u*, given by u* = h1k √( K/µ), where h1 is the initial waviness amplitude, K is the wave number (κ = π/Λ, where Λ is half the wavelength of a sinusoidal waviness), K is the thermal conductivity of the metal, μ is the fluid viscosity, and α is the coefficient of expansion. Past experience has shown that the product h1 k is such that long-wavelength waviness is associated with the lowest u* and therefore magnified relative to shorter wavelength components of the surface topography. Thermal deformations appear to be favourable in their influence on film thickness—except where the unexplained but experimentally observed transition to point contact occurs.
The Influence of Surface Roughness on Friction and Wear in Boundary Lubrication
Authors: Hisakado T.
Published: February 2007

Assuming that the radii of curvature at tips of spherical asperities are distributed, analyses of friction and wear in boundary lubrication are carried out by considering the ploughing action of hard asperities. To check the theory, the coefficient of friction and the wear rate of an annular end surface of a mild-steel cylinder rubbed by that of a hardened-steel cylinder are measured for various degrees of roughness from 0.038 to 0.568 μ Rmax under lubricated conditions. The general trend of the experimental results is in agreement with the calculations. The results also indicate that the repetition of the ploughing action of hard asperities forms the wear particles.
Calculation of the Topographic Characteristics of Rough Surfaces by Virtue of Profile
Authors: Demkin N. B. , Korotkov M. A.
Published: February 2007

It is shown that the relationship between surface characteristics and profile may be found by modelling the surface with a number of peaks, geometrically perfect and height-distributed, so that the distribution of material in the model of a rough layer corresponds to a real surface.
Heat Transfer in the Entrance Region of Tubes that Rotate about a Parallel Axis
Authors: Morris W. D. , Woods J. L.
Published: February 2007

The paper presents the results of an investigation into the effect of rotation on heat transfer in the entrance region of circular tubes that are constrained to rotate about an axis parallel to the symmetry axis. This rotating geometry is an important feature of flow systems designed for cooling the rotor windings and armature drums of electrical machines and other prime movers. It is demonstrated that rotation tends to improve local and mean heat transfers, and correlating equations are proposed for turbulent and laminar flows.
A Study of Fully-Developed, Laminar, Axial Flow and Taylor Vortex Flow by Means of Shear Stress Measurements
Authors: Coney J. E. R. , Simmers D. A.
Published: February 2007

The results of a shear stress investigation for combined axial and rotational flow, under conditions of both laminar flow and laminar flow plus Taylor vortices, are presented. These results show that two distinct régimes of shear stress dependency exist. In the primary régime, the shear stress is constant and depends only on the imposed axial flow, the flow being either laminar (Poiseuille and Couette flows) or laminar with vortices, but with the effect of the vortices being negligible. In the secondary régime, the shear stress is shown to depend only on Ta0.735, irrespective of the imposed axial flow. At low axial flow rates, a tertiary régime was observed, but no satisfactory explanation can be found for this phenomenon. The demarcation between the primary and secondary flow régimes differs markedly from those of other investigators. In the present study, critical conditions are determined by the point at which vortices begin to have an effect on measurements taken at the outer annular wall rather than the conditions under which vortices are initially formed. Evidence is presented for the vortices being formed within a confined layer near to the inner cylinder and thereafter growing with increasing rotational speed until the outer annular wall is approached, resulting in the much higher critical conditions found in the present study.
The Effect of Taylor Vortex Flow on the Development Length in Concentric Annuli
Authors: Simmers D. A. , Coney J. E. R.
Published: February 2007

Results are presented of an investigation into a developing, combined axial and rotational flow in an annular gap formed by a stationary outer cylinder and a rotatable inner cylinder for an annulus radius ratio of 0–8 and an axial Reynolds number of 1200.

These results show that, in the Taylor vortex flow régime, the development length decreases with the parameter Re2a/Ta and that the greatest development length in an annular gap, for a given axial Reynolds number, occurs when the Taylor number is near to its critical value.

Consideration of isothermal heat transfer through the outer wall of the annular gap suggests that, in the development of the flow, the Nusselt number rises to a high value before falling to a constant value, at full development.
Parameter Plane Studies of Car-Steering Stability with Combined Lateral and Previewed Error-Sensing by the Driver
Authors: Thompson A. G.
Published: February 2007

Parameter plane curves of the driver's minimum preview distance for stability ( P) versus his gain ( KD) are derived. These curves represent the boundaries for absolute or relative stability of the complete car—driver system. The driver's error input is assumed to be a weighted sum of his lateral position error and predicted error at the preview distance, P. This results in a simple steering strategy which, in simulation studies, will permit the car to be driven on winding roads.

Part 1 is restricted to straight roads and compares the parameter plane and gain-crossover theories. Tracking accuracy in a steady turn is improved by a steering strategy in which the driver acts on both the lateral and previewed errors. It is shown that the lateral error becomes zero if the preview, P, equals an optimal value, Pm, depending on the speed and radius of the turn. The stability plots for straight roads are adapted to the determination of stability in turns. A computer simulation of a car driven on a road S-bend provides information on stability, tracking accuracy and optimal preview distances which correlate with the results of the other studies in Part 2.
An Experimental Method for the Determination of Journal-Bearing Stability Parameters. Part 1: Theory
Authors: Marsh H. , Simmons J. E. L.
Published: February 2007

In the design of a rotor-bearing system, information is usually available on the steady-state performance of the bearing. The designer can estimate the eccentricity ratio and attitude angle for any operating condition, but there is often little or no information which can be used to predict whether or not this is a stable operating condition. This paper describes the basic theory of bearing stability and shows how this can be used to help in the design of a novel apparatus for determining the stability parameters of any journal-bearing system.
Nonlinear Behaviour of Unsymmetric, Angle-Ply, Rectangular Plates under in-Plane Edge Shear
Authors: Prabhakara M. K. , Kennedy J. B.
Published: February 2007

A nonlinear analysis of unsymmetric, angle-ply, rectangular plates under uniform in-plane edge shear is presented. The solution is based on the von Kármán-type large-deflection equations, with the force function and the transverse deflection expressed as double series in terms of appropriate beam functions. The prescribed boundary conditions, including those for the vanishing of normal bending moment at the edges of simply supported plates, are satisfied. Numerical results for the buckling loads and for the post-buckling deflections, membrane forces and bending moments are presented for plates composed of high-modulus, fibre-reinforced epoxy composites.
Studies of the Depressurization of Gas-Pressurized Pipes during Rupture
Authors: Baum M. R. , Butterfield J. M.
Published: February 2007

Measurements are presented of the initial rates of depressurization generated within ductile steel pipes in pneumatic rupture tests. The breach was initiated by failure of an axial, part-through, flat-bottomed defect machined in the outer surface of the pipe.

The measured depressurization rates for supercritical defects are shown to be in agreement with values predicted by a theoretical model which assumes that the pipe hinges open. Where the initial defects are longer than two pipe diameters, the extent of the hinging section is defined by the initial defect length. For short initial defects, a significant breach does not develop until the defect has propagated axially to a length of the order of two pipe diameters, and hence the effective hinging length is two pipe diameters Initial depressurization rates for subcritical defects correlate with the Folias bulging parameters.
Predicting Crack-Formation Life
Authors: Duggan T. V. , Lowcock M. T. , Staples B. C.
Published: February 2007

This paper discusses the parameters likely to influence the crack-formation life of components. In particular, the relationship between the fatigue life of plain and notched specimens is considered, and a mathematical model for predicting the crack-formation life of components is proposed. This allows for the effects of mean stresses and strains and is dependent upon the determination of local material behaviour. The approach is original in that it makes allowances for the influence of the degree of plasticity around a notch, represented in terms of the strain gradient. The Neuber method is evoked, suitably modified to allow for strain gradient effects, and strain gradients are estimated by differentiating Neuber's rule in the immediate vicinity of the notch.

Experimental studies have been conducted to determine strain distributions, strain gradients and cyclic lives, and the results compared with predicted values; correlation is good.
The Influence of Axial Profile on Pressure Distribution in Radially Loaded Rollers
Authors: Heydari M. , Gohar R.
Published: February 2007

Numerical solutions are given for the pressure distribution and footprint shape of a roller in a roller bearing subjected to both radial load and misalignment. The method used makes it possible to profile the rollers axially until the longitudinal pressure distribution is either almost uniform or does not have any severe peaks, thereby increasing the bearing service life.
Experimental Evaluation of the Predicted Behaviour of Squeeze-Film-Bearing-Supported Rigid Rotors
Authors: Simandiri S. , Hahn E. J.
Published: February 2007

This paper describes the experimental investigations which were conducted to verify existing theoretical vibration-amplitude predictions for centrally-preloaded, squeeze-film-bearing-supported rigid rotors. Very good agreement was obtained with all aspects of these predictions, including the degree of pressurization needed to achieve full-film lubrication and the complicated bistable operation behaviour. By developing the theoretical model for the more general case of a rigid rotor supported by unequal squeeze-film bearings at the ends, it is shown how existing theoretical data, derived on the basis of a symmetric rotor with symmetric motion, are readily applicable to the case of a rotor supported by squeeze-film bearings at one end only. The experimental rig consisted of such a rotor, and, although the results are based on a given bearing having a length-to-diameter ratio of 0.167, and did not allow for any significant variation in the radial support stiffness, nor for variation in the bearing dimensions, and the rotor speed did not exceed 7500 rev/min, it is concluded that the theoretical data predictions are valid in general. Their validity is questionable, however, should conditions be such that turbulence and/or unaccounted-for cavitation effects become significant. Squeeze-film bearing behaviour under such conditions warrants further investigation.
Effects of Axial Assembly Stress in Compound Cylinders
Authors: Cole B. N. , Parsons B.
Published: February 2007

Sometimes negligible and sometimes not, axial assembly stresses in compound pressure vessels continue to be largely ignored. The paper offers an approximate analysis of the manners in which these stresses may arise, and describes their final distributions, for the two cases of force-fit and shrink-fit assembly. Possible implications for the pressure vessel when in service are discussed.
Dynamic Characteristics of Aerostatic Thrust Bearings with Porous Inserts
Authors: Majumdar B. C.
Published: February 2007

A first-order perturbation method is adopted to find the dynamic behaviour of an aerostatic circular thrust bearing having a central porous insert as a restrictor. The linearized gas film stiffness and damping are derived and used to study their behaviour with other design variables.
The Effect of Combined Coning and Waviness on the Separating Force in Mechanical Face Seals
Authors: Etsion I.
Published: February 2007

A mechanical seal model having face geometry of combined waviness and coning is analysed. A closed form analytical solution for the pressure in the lubricating film and the axial separating force is presented, covering the complete range of waviness and coning. The separating force is found to be linearly dependent on the number of waves and strongly affected by coning. A comparison with a seal model having angular misalignment combined with coning reveals that in both models the separating force is essentially of the same order of magnitude.
A Theory of Contact Loss at Resolute Joints with Clearance
Authors: Haines R. S.
Published: February 2007

Equations are derived that describe the conditions at a general idealized revolute joint, with clearance but with no hydrodynamic lubrication present. The equations are governed by three dimensionless parameters that depend on the nominal motion, mass distribution and influence coefficients of the linkage in which the joint appears, as well as the clearance magnitude. A series of numerical solutions of the equations is used to predict the conditions under which contact is lost, leading to impacts. The results are presented in the form of a design chart and the implications are discussed.
The Measurement of the Radial Stiffness of Rolling Element Bearings under Oscillating Conditions
Authors: Walford T. L. H. , Stone B. J.
Published: February 2007

There is very little information available on the characteristics of rolling element bearings under oscillating conditions. This is because of the difficulty that has been experienced in measuring the relevant characteristics. A rig is described which is very simple in principle and allows the measurement of the radial stiffness of a pair of bearings. For the angular contact bearings tested the levels of damping obtained are larger than previously expected.
The Elastohydrodynamic Lubrication of Heavily Loaded Point Contacts
Authors: Hooke C. J.
Published: February 2007

It is shown that the film thickness in heavily loaded point contacts can be accurately calculated by comparing the inlet and exit zones of the contact with those of an equivalent line contact. The results become increasingly accurate as the extent of the inlet and exit regions is reduced and in the limit yields an exact solution. Even for moderately loaded contacts in which the inlet zone occupies a substantial part of the contact width the results are in close agreement with existing numerical solutions.
The Angle of Fold and the Plastic Work Done in the Folding of Developable Flat Sheets of Metal
Authors: Johnson W. , Yu T. X.
Published: February 2007

Under the condition of inextensibility, an initially flat sheet of metal can be folded along straight lines or a curved line to produce various surfaces. The angle of fold and the plastic work done in folding along a line are examined for a series of cases, such as folding-up into a prism and a frustum, folding on a cylinder along a circular arc, and more generally, folding on a developed surface along an arbitrary curved line. Some numerical results are given.
Dynamic Total Head Loss Characteristic for an Axial Compressor Rotor
Authors: Sharma P. B. , Railly J. W.
Published: February 2007

Detailed flow field and pressure measurements during rotating stall operation have been carried out at inlet to and exit from an axial compressor rotor using hot wire anemometers and probes incorporating fast response pressure transducers. An on-line data-acquisition system which employs a phase-lock sampling and averaging technique has been used to obtain ‘phase-lock averaged’ values of flow quantities and pressures. The dynamic total head loss/incidence characteristic for the rotor section at mean diameter has been computed from the above data. The dynamic characteristic exhibits a loop in the stalled region. A simple numerical procedure has been used to obtain the steady-state loss characteristic and the time-lag of this loss. It has been found that the loss time-lag of boundary layer time delay corresponds to a value equal to 1.8 times the time delay due to inertia of fluid in a blade passage. A simple theory for the prediction of this loss time-lag is also presented which shows reasonable agreement with the value determined from measurements.
Bending of Long Steel and Aluminium Rods during end Impact with a Rigid Target
Authors: Reid S. R. , Edmunds A. J. , Johnson W.
Published: February 2007

Bless and Barber (1) ‖ have shown that rod projectiles can be affected by the propagation of bending deformation along their lengths when they strike rigid targets at sub-ordnance velocities. Experiments are described in which a range of different modes of deformation are identified for both normally and obliquely incident steel and aluminium rods of length to diameter ratio 24 : 1. The results are discussed from the point of view of classical dynamic structural plasticity.
An Analogue Simulation of the Nonlinear Vibration of a Plate with a Central Opening Subjected to Tension Loading
Authors: Datta P. K.
Published: February 2007

The complicated, nonlinear stiffness characteristics of a tensioned plate with a central opening are studied via analogue computer simulation. Associated frequency response characteristics and statistical properties of the response to random excitation are examined using a single degree of freedom model.
A Method for Predicting Annular Diffuser Performance with Swirling Inlet Flow
Authors: Elgammal A. H. , Elkersh A. M.
Published: February 2007

A method for predicting the performance of annular diffusere with swirled flow at inlet is presented. The method is based on the assumptions of one-dimensional potential flow using a frictional coefficient parameter to account for friction losses. Theoretical predictions are in good agreement with available experimental data for a variety of annular diffuser geometries. In addition a computer program has been developed, allowing the present analytical technique to be readily applied to the design of any annular diffuser with swirled flow at inlet.
Velocity Fluctuation in Spatial Four-Link Mechanisms
Authors: Osman M. O. M. , Dukkipati R. V.
Published: February 2007

This paper presents an algebraic solution of the velocity fluctuation in a spatial four-link mechanism. The geometric conditions governing the existence of extreme velocity ratios in a spatial four-link mechanism having one revolute pair, one prismatic pair, one spherical pair, and one cylinder pair have been obtained. It is shown that, in the general case, the extreme velocity ratios must be among the real roots of a tenth degree polynomial in kinematic parameters of the mechanism. Numerical examples are presented to illustrate the described procedure.
Simulation of Viscous Diffusion for Extension of the Surface Vorticity Method to Boundary Layer and Separated Flows
Authors: Porthouse D. T. C. , Lewis R. I.
Published: February 2007

A numerical method for two-dimensional incompressible viscous fluid flows is tested on the diffusion of a point vortex. It is then applied to the boundary layer to reconstruct the Blasius profile, to demonstrate flow separation, and to simulate turbulence. The significance of Thwaites' boundary layer parameter for flow separation is explained. The Kelvin-Helmholtz instability, which is responsible for two-dimensional turbulence, is represented by the motion of an array of point vortices after an initial disturbance. The formation of the Von Karman vortex street downstream of a circular cylinder is described by computer simulation, and the influence of viscous diffusion is shown. For two different cylinder Reynolds numbers the vortex shedding frequencies and oscillating lift and drag forces are evaluated.
Modified Pivotal Plot for Critical Load Calculation of a Rectangular Plate under Edge Compression
Authors: Chau Fok Wing , Fai Yuen Ming
Published: February 2007

The paper presents a method of estimating the experimental critical load and initial imperfection of a rectangular plate under edge compression from the load deflection measurement. By using the concept of ‘Pivotal Points’ the load deflection results are plotted in a straight line form where the intercept gives the critical load and the slope is the initial imperfection. Initial imperfection up to thickness of the plate can be handled.

The method was applied to various published data and was shown to give accurate results.
The Prediction of Gas Pressures within the Ring Packs of Large Bore Diesel Engines
Authors: Ruddy B. L. , Dowson D. , Economou P. N.
Published: February 2007

The established orifice and volume method for predicting the gas pressures between piston rings in reciprocating machines is extended to take account of the energy loss due to wall friction in the circumferential gas flow between the piston and cylinder liner.

The results show that such energy losses are significant when gas flow rates exceed 10-2 kg/s and that this is most likely to occur in engines of over 0·5 m bore with worn piston rings. Under these conditions the angular displacement of the ring gaps significantly affects ring pack gas flow. In particular, it is shown that the maximum resistance to the flow of gas through the ring pack occurs when adjacent ring gaps are separated by more than 90 degrees.

In the analysis of piston ring lubrication in ring packs it is necessary to ascertain the inter-ring pressures and the present paper enables such pressures to be determined with greater accuracy and for a wider range of engines.
An Analysis of the Squeeze Film between Porous Rectangular Plates Including the Surface Roughness Effects
Authors: Prakash J. , Tiwari K.
Published: February 2007

The paper describes a theoretical analysis of the effects of unidirectional surface roughness on the response of a squeeze film between two porous rectangular plates of finite dimensions. The problem is solved analytically using Fourier expansions. It is shown that the nominal geometry as characterized by the aspect ratio of the plates has a profound effect on the system.
Minimizing the Thermal Resistance of Pressed Contacts
Authors: Snaith B. , O'Callaghan P. W. , Probert S. D.
Published: February 2007

A procedure is described for predicting the recommended insert thickness which will result in minimizing the thermal resistance of a pressed contact between fiat, non-wavy, surfaces. The analysis is based upon the assumption of ideal plastic asperity deformations occurring at the interfaces formed between randomly high rough surfaces and the insert material. Experimental measurements of the thermal resistances for aluminium-tin-aluminium and stainless steel-tin-stainless steel, mechanically loaded assemblies corroborate within experimental error the predictions from the theory, and hence validate the analysis.
Parametric Instability of Tapered Beams by Finite Element Method
Authors: Datta P. K. , Chakraborty S.
Published: February 2007

The dynamic stability behaviour of a tapered beam has been studied using a finite element analysis. The instability zones of the parametric stability diagram have been discussed for the entire ranges of static and dynamic load factors. It has been observed that at high values of static load and beyond a particular value of the dynamic load factor, the periodic solution of the Mathieu equation does not exist in the principal region. This leads to unstable behaviour due to large displacement of the beam due to increasing values of static and dynamic load factors.
Dynamic Stability of Wave-Convection Transport
Authors: Greenberg M. D. , Harrell C. Y.
Published: February 2007

A flexible inextensible horizontal belt is assumed to be formed, by closely spaced vertical push rods, into a traveling sine wave. A spherical object resting at the bottom of a trough will tend to be convected with the trough as the wave travels. The dynamic stability of such wave-convection transport is considered. Assuming the wave to be shallow, the governing nonlinear equations are expanded (through second order) in the ‘shallowness parameter’, and thus reduced to a single equation, essentially of forced Duffing type, which is integrated numerically, over the parameter space of practical interest, to yield a stability criterion.
Photocatalytic Steam Reforming of Methane over Platinum-loaded Semiconductors for Hydrogen Production
Authors: Yoshida Hisao , Kato Satoru , Hirao Kazuhisa , Nishimoto Jun-ichi , Hattori Tadashi
Published: February 2007

Hydrogen can be photocatalytically produced from methane and water by using platinum-loaded semiconductor photocatalysts. Platinum-loaded lanthanum-doped NaTaO3 (Pt/NaTaO3:La) showed higher photocatalytic activity for this reaction than platinum-loaded TiO2 did. The apparent quantum yield of this system employing Pt/NaTaO3:La was estimated to be higher than that of photocatalytic water splitting system employing NiO/NaTaO3:La.
Preparation of Bowl-like Hexagonal ZnO Nanostructures by a Template-assisted Solvent-thermal Route
Authors: Zhao Aiwu , Liang Jianbo , Xiong Zhenglin , Qian Yitai
Published: February 2007

Bowl-like ZnO nanostructures with hexagonal shape have been fabricated by a solvent-thermal synthesis route with the assistance of ultrathin anodic aluminum oxide (AAO) template. Transmission electron microscopy and high-resolution transmission electron microscopy investigations confirm that the bowl-like ZnO structures are single-crystalline. The room temperature photoluminescence investigation shows that the products have a sharp near band-edge emission and another broad green emission band centered at 386 nm and around 525 nm, respectively.
Blue-emitting Type-II Semiconductor Nanocrystals with High Efficiency Prepared by Aqueous Method
Authors: Li Chunliang , Nishikawa Kazuhiro , Ando Masanori , Enomoto Hiroyuki , Murase Norio
Published: February 2007

Forming a type-II structure on alloyed ZnSe core through a facile aqueous method using Cd and S ions resulted in nanocrystals with a photoluminescence wavelength adjusted to the blue region. Their surface was additionally coated by wider band-gap ZnS shell through photodecomposition of the surfactant molecules. Optimizing the conditions for creating the core and shells increased their emission efficiency more than 40%.
RuO2-loaded Sr2+-doped CeO2 with d0 Electronic Configuration as a New Photocatalyst for Overall Water Splitting
Authors: Kadowaki Haruhiko , Saito Nobuo , Nishiyama Hiroshi , Inoue Yasunobu
Published: February 2007

Ruthenium oxide-loaded Sr2+-doped CeO2 with f0d0 electronic configuration was found to have photocatalytic activity for overall water splitting into H2 and O2 under UV irradiation, whereas neither undoped CeO2 nor stoichiometric compounds such as SrCeO3 and Sr2CeO4 was photocatalytically active.
Unexpected Spiro-benzoquinolines in the Reaction of N-(Arylidene)naphthalen-2-amine, Arylaldehyde, and 1,3-Dimethylbarbituric Acid in Water
Authors: Wang Xiang-Shan , Zhang Mei-Mei , Jiang Hong , Yao Chang-Sheng , Tu Shu-Jiang
Published: February 2007

A series of unexpected pyrimidine spiro-benzoquinolines were developed based on the reaction of N-(arylidene)naphthalen-2-amine, arylaldehyde, 1,3-dimethylbarbituric acid in aqueous media catalyzed by triethylbenzylammonium chloride (TEBAC). The structure of the product 4a was confirmed by X-ray diffraction studies. In addition, the water was chosen as green solvent.
Uniqueness and Stability of Optimal Policies of Finite State Markov Decision Processes
Authors: Leizarowitz Arie , Zaslavski Alexander J.
Published: February 2007

In this paper we consider infinite horizon discrete-time optimal control of Markov decision processes (MDPs) with finite state spaces and compact action sets. We restrict attention to unicost MDPs, which form a class that contains all the weakly communicating MDPs. The unicost MDPs are characterized as those MDPs for which there exists a solution to the single optimality equation. We address the problem of uniqueness and stability of minimizing Markov actions. Our main result asserts that when we endow the set of unicost MDPs with a certain natural metric, under which it is complete, then the class of MDPs with essentially unique and stable minimizing Markov actions contains the intersection of countably many open dense sets (hence is itself dense). Thus, the property of having essentially unique and stable minimizing Markov actions is generic for unicost MDPs.
Lagrange Multipliers in Nonsmooth Semi-Infinite Optimization Problems
Authors: Zheng Xi Yin , Yang Xiaoqi
Published: February 2007

Using the variational analysis technique, in terms of the epi-coderivative, we provide Lagrange multiplier rules for a class of semi-infinite optimization problems where all functions are lower semicontinuous or locally Lipschitz.
The relative importance of task, citizenship and counterproductive performance to job performance ratings: Do rater source and team‐based culture matter?
Authors: Lievens Filip , Conway James M. , De Corte Wilfried
Published: February 2007

This study contributes to our understanding of which factors predict raters' policies for combining performance components into an overall job performance rating. We used a work‐roles framework to examine the effects of rater source and team‐based culture. The sample consisted of 612 individuals in three job categories (317 nurses, 168 personnel recruiters and 127 sales representatives). Respondents rated employee performance profiles that were described on task, citizenship and counterproductive performance. Raters' weights differed by (a) organizational culture (low‐ vs. high‐team‐based); (b) rating source (supervisor vs. peer) and (c) job. In a team‐based culture, more weight was given to citizenship performance and less to task performance. Peers attached more importance to citizenship performance and less to task performance. Implications of these findings for performance management are discussed.
Einleitung/Editorial
Authors: Brennecke Hanns Christof
Published: February 2007

Nun schon zum dritten Mal ist das erste Heft eines Jahrganges der ZAC einem besonderen Thema gewidmet, in diesem Jahr, wie bereits in 9/1 angekündigt, Athanasius von Alexandrien.
Das Evangelium des Judas
Authors: Plisch Uwe-Karsten
Published: February 2007

Einleitung

Der nun als Codex Tchacos bekannt gewordene Papyruscodex kursierte seit etwa einem Vierteljahrhundert auf dem Antiquitätenmarkt und wird nun unter der Leitung des renommierten Schweizer Koptologen Rodolphe Kasser erschlossen. Er enthält insgesamt vier ursprünglich griechisch verfasste Texte in koptischer Übersetzung; neben dem Evangelium des Judas als dritter Schrift den „Brief des Petrus an Philippus“ und die „Erste Apokalypse des Jakobus“, die beide bereits aus dem Handschriftenfund von Nag Hammadi bekannt sind (Nag-Hammadi-Codex VIII,2 und V,3) sowie am Schluß einen kurzen Text, dessen Titel nicht erhalten ist und in dem die schon aus NHC XI,3 geläufige Bezeichnung „Allogenes“ für den Erlöser eine herausragende Rolle spielt. Der Codex stammt wahrscheinlich aus dem 4. Jahrhundert und ist damit etwa ebenso alt wie die Codizes des Nag-Hammadi-Fundes.
Athanasius und Basilius
Authors: Heil Uta
Published: February 2007

The author shows the authenticity of two letters of Athanasius, the Epistula ad Palladium and the Epistula ad Joannem et Antiochum. They belong to the later period of Athanasius' life and are vestiges of the broad correspondence of Athanasius which is now lost. In these letters Athanasius utters strong support for his colleague Basilius of Caesarea, although they do not agree in doctrinal matters. This is no reason, however, to believe that those letters are forgeries of later times. The author shows the historical context of the two letters and provides an overview of the last years of Athanasius.