bluuebunny/crossref_metadata_2025_split huggingface dataset:
On flexure-torsion flutter criteria
Authors: Simpson A. 
Published: July 2016

AbstractThe classical criteria of the 1920s for the avoidance of flexure-torsion flutter were based on parameters such as stiffness ratio and the position across the typical chord of the aerodynamic, elastic and mass centres.In more recent times, and in the context of aeroelastic tailoring of lifting surfaces constructed with composite materials, a new terminology has emerged — as evident from technical papers produced in the USA over the past decade. The prevention of flexure-torsion flutter, or the raising of the critical speed, is now achieved by providing morewash-inor lesswash-out, where these terms do not have their established aeronautical meanings — and for this reason (and other, non-semantic ones) are to be deprecated.By recourse to a typical section model (with quasi-steady and unsteady compressible aerodynamics), the writer argues that, for conventionally constructed wings, the new criteria are ‘fuzzy’ and incomplete versions of the earlier criteria in respect of the positioning of the various ‘centres’ (i.e.,elastic, mass and aerodynamic)across the typical chord, and therefore that the new terminology is redundant in this context.For laminated composite wing structures, even when the construction is uniform and the fiexural axis straight, it is established that the inclination of this axis with respect to the CG and aerodynamic axes may be so large that the fiexural and shear centres at the tip could be several chords forward or aft of the mid-chord axis; the criteria of the 1920s are then irrelevant. The wash-in/wash-out criteria may then be said to ‘come into their own’, albeit that it is shown herein that they remain fuzzy and incomplete — even for quasisteady binary problems. A crude modal binary model of a rudimentary laminated composite wing is included to illustrate this and other features. By recourse to a higher-order flutter formulation, the writer demonstrates that the wash-in/wash-out criteria are, in certain respects, unreliable.
Incorporation of manufacturing information into an MDO environment
Authors: Gantois K. , Morris A. J. 
Published: July 2016

AbstractThe Paper describes a metal and composite recurrent cost model of a large civil aircraft wing structure for a multidisciplinary design, analysis and optimisation (MDO) environment. The work was part of a recent European MDO project (BE95-2056) which investigated methods for the integration of structures, aerodynamics, dynamics and manufacturing cost at the preliminary design stage.The paper discusses the cost modelling approach, which is based on parametric and process cost model methods, and the integration of the cost models into an MDO process. Results for the cost models are shown.A framework has been successfully developed which allows the incorporation of manufacturing cost models into an MDO environment. It allows a designer to evaluate cost changes with respect to specific design changes such as rib pitch, stringer pitch, wing area and wing sweep.
Sequential use of conceptual MDO and panel sizing methods for aircraft wing design
Authors: Butler R. , Lillico M. , Banerjee J. R. , Patel M. H. , Done G. T. S. 
Published: July 2016

AbstractThe optimisation results for composite and metallic versions of a regional aircraft wing are compared using the multidisciplinary optimisation (MDO) program CALFUNOPT. The program has been developed for the conceptual design stage and models the wing using just 11 beam elements. The wing has been optimised for three combinations of the following constraint cases: static strength; aeroelastic roll efficiency (represented by limiting the twist of the wing for an aileron loading) and aeroelastic divergence. As expected, comparison shows that the composite wing designs are significantly lighter than the metallic ones, due to the well-known tailoring of the composite material. However, the simple model reveals some insight that may be useful to the designer, and which could be lost within a more detailed finite element approach.The upper-skin compression panels produced by the conceptual MDO program, for both versions of the wing, have then been optimised using the more detailed and accurate panel sizing tool VICONOPT, which takes buckling into account. Such optimisation increases the panel mass by 5-10% and also provides a suitable ratio of stiffener to skin area for use in the conceptual MDO model.
Prediction of tunnel wall upwash for delta wings including vortex breakdown effects
Authors: Traub L. W. 
Published: July 2016

AbstractAn incompressible method is presented to predict the upwash corrections associated with vortical flow as a result of wind-tunnel side wall effects. An image system is used to simulate the tunnel side walls which are assumed to be solid. An integral expression is formulated, representing the average upwash induced over the wing by the image system. Wall effects may be determined for flows with and without vortex breakdown. Comparisons of the results with upwash predictions from a Navier-Stokes study show close accord. The upwash expression also displayed the ability to successfully predict corrections for flows involving vortex breakdown.
Two and three component velocity measurements in a wind tunnel using PIV
Authors: Bearman P. W. , Harvey J. K. , Stewart J. N. 
Published: July 2016

AbstractThis paper describes the development of particle image velocimetry (PIV) to measure instantaneous spatial distributions of velocity in flows generated around models in a low speed wind tunnel with a test section 3m wide by 1·5m high. The difficulties associated with using PIV in air at this scale, and how they can be overcome, are discussed. Stereoscopic PIV is used to correct errors due to parallax that are present in velocity components measured in the plane of a light sheet when there is an accompanying flow through the sheet. This technique is also used to measure all three components of velocity in planes across a flow. It is found that apparently good estimates of a mean flow field can be obtained by averaging as few as ten instantaneous measurements of the flow field. The flows studied are generated by a 1/8 scale model of an aircraft for which the wing sweep can be varied. Measurements of velocities associated with the main vortex structures generated over the wing are presented for a sweep angle of 70°. Measurements of velocities recorded in the wake of a large fuel tank mounted below the wing, for a wing sweep of 45°, are also shown.
An eddy-viscosity limited algebraic stress model for shock-boundary-layer interaction
Authors: Richardson G. , Qin N. 
Published: July 2016

AbstractThis paper presents a μt-limited explicit algebraic stress model for shock-wave-turbulent boundary-layer interactions based on an investigation of various two-equation turbulence models. The results of the κ-ω model, the shear stress transport (SST) model, and a quadratic explicit algebraic stress model are presented and analysed for the Delery channel bump, and the Bachalo and Johnson axisym-metric bump test cases. While the κ-ω model failed to give good predictions, the SST model proved reasonably successful in predicting strong interaction problems. The non-linear quadratic explicit algebraic stress model gave improved results (when compared with the original κ-ω model) for the channel bump test cases, but was not as good as the SST model. Inspired by this investigation, a model formulation is proposed in which Bradshaw's assumption for eddy-viscosity limiting (as used in the SST model) is applied to a quadratic explicit algebraic stress model. The QSST model further improves the SST model for strong shock-boundary-layer interactions.
Effect of Mach number on the acoustic field of 2:1 elliptic-slot jet
Authors: Verma S. B. , Rathakrishnan E. 
Published: July 2016

AbstractThe shock-structure and the related acoustic field of underexpanded jets undergoes significant changes as the Mach number Mj is increased. The present investigation is carried out to study the effect of Mach number on an underexpanded 2:1 elliptic-slot jet. Experimental data are presented for fully expanded Mach numbers ranging from 1.3 to 2.0. It is observed that the ‘cross-over’ point at the end of the first cell at low Mach numbers gets replaced by a normal shock at a highly underexpanded condition resulting in the formation of a ‘barrel’ shock along the minor-axis side with a ‘bulb’ shock formed along the major-axis side. The above change in shock structure is accompanied by a related change in the acoustic field. The amplitude of fundamental frequency along the minor-axis side grows with Mj but falls beyond Mj = 1.75. Along the major-axis side, however, the fundamental frequency does not exist at low Mach numbers. It appears at Mj = 1.75 but then falls at Mj = 2.0. The related azimuthal directivity of overall noise levels (OASPL) shows significant changes with Mj.
Extract from A Wrack Behind: Cardington
Authors: Norton Lord Kings 
Published: July 2016

The performance of German airships during the war, and the double crossing of the Atlantic by the airship R34 in 1919, sufficiently impressed the Air Ministry that it embarked on a British airship programme which produced R38 and R80. The Ministry was undoubtedly deterred by the appalling R38 disaster in 1921 but, presumably as a result of Professor Bairstow’s demonstration of the inexcusable inadequacy of the R38 design, they did not abandon their plans. After all R80, to the design of B.N. Wallis, the great engineer who became famous as Sir Barnes Wallis after the 1939-45 war, had been a success.So in 1924 the Air Ministry decided to order two airships, each of five million cubic feet capacity. One, to be called R100, was ordered from the Airship Guarantee Company, a Vickers subsidiary headed by Sir Denniston Burney. It was to be built at Howden. The other, to be called R101, was to be built by the Air Ministry itself, at the Royal Airship Works, Cardington. At the head of the Burney design team was B.N. Wallis. At the head of the Air Ministry design team was V.C. Richmond.
Extract from A Wrack Behind: Frank Whittle
Authors: Norton Lord Kings 
Published: July 2016

Whittle is one of the great engineers of the century, perhaps the greatest if judged by the scale of the consequences of his invention. Only the discoverer of the properties of the silicon chip could claim comparable importance.Jet propulsion was first demonstrated by Hero of Alexandria in AD 60. The gas turbine was patented by Barber of Nuneaton in 1791. Whittle patented a design for an aircraft engine in 1930 in which propulsion was to be achieved by a jet produced by a gas turbine. By combining the thoughts of two men separated in time by over 1,700 years he made an engine which revolutionised world air transport.
Extract from A Wrack Behind
Authors: Lord Kings Norton 
Published: July 2016

In 1943, with the world still at war, a great discussion on the future of aeronautical education was held by the Royal Aeronautical Society. Not only would the war years, however many were still to come, demand more well-qualified aeronautical engineers, but the longed for peace years, with engineers turning swords into ploughshares, would want more. The discussion was in two parts. One took place on 25 June and the other on 23 July. Many of the leading figures in British aeronautics took part and in the chair on both occasions was Dr Roxbee Cox, a vice-president of the society. The discussion culminated in a resolution based on a proposal by Marcus Langley. That resolution and the discussion which led to it resulted in the recommendation by the Aeronautical Research Committee that a post-graduate college of aeronautical science should be established. This was followed by governmental action. Sir Stafford Cripps, then the minister responsible for aircraft production, set up a committee presided over by Sir Roy Fedden to make specific proposals, and the committee recommended in its 1944 report that such a college should be a new and independent establishment. In 1945 the government created the College of Aeronautics board of governors under the chairmanship of Air Chief Marshal Sir Edgar Ludlow-Hewitt to bring the college into existence and govern it. The first meeting of this board took place on 28 June 1945 and there were present:Sir Edgar Ludlow Hewitt, Dr W. Abbot, Mr Hugh Burroughs, Sir Roy Fedden, Mr J. Ferguson, Sir Harold Hartley, Sir William Hil-dred, Sir Melvill Jones, Dr E.B. Moullin, Mr J.D. North, Sir Frederick Handley Page, Mr E.F. Relf, Dr H. Roxbee Cox, Air Marshal Sir Ralph Sovley, Rear Admiral S.H. Troubridge and Mr W.E.P. Ward. Sir William Stanier, who had been appointed, was not present.
Extract from A Wrack Behind: Myself, when old
Authors: Norton Lord Kings 
Published: July 2016

I am not quite sure when I became old, but I think I must date it in my seventies when I retired from a variety of activities and settled into a more sedentary style of life. I retired from Dowty Rotol and Bergers (and so Hoechst UK) in 1975, from the Royal Institution in 1976, from Ricardo’s and British Printing Corporation in 1977 and sold Withers Estates, very profitably for the Withers family, in 1981.I was left with the chairmanships of two tiny companies, Land-speed and Cotswold Research. While Landspeed has not served its purpose, Cotswold Research has its place in history. Both companies are concerned with the inventions of Professor Eric Laithwaite, who demonstrated in model and prototype form tracked hovercraft powered by the linear motor. Landspeed failed to develop this, through lack of funds, to a commercially viable transport system, though the Japanese appear to have done so. Cotswold Research, however, made a success of an adaptation of the linear motors to the separation of aluminium from scrap material and for their work, which ended in profitable industrial apparatus and a big saving in manpower, Mr A.P. Bird and I received the Prince of Wales Award in 1986.
The evidence for open and closed exocytosis as the primary release mechanism
Authors: Ren Lin , Mellander Lisa J. , Keighron Jacqueline , Cans Ann-Sofie , Kurczy Michael E. , Svir Irina , Oleinick Alexander , Amatore Christian , Ewing Andrew G. 
Published: July 2016

AbstractExocytosis is the fundamental process by which cells communicate with each other. The events that lead up to the fusion of a vesicle loaded with chemical messenger with the cell membrane were the subject of a Nobel Prize in 2013. However, the processes occurring after the initial formation of a fusion pore are very much still in debate. The release of chemical messenger has traditionally been thought to occur through full distention of the vesicle membrane, hence assuming exocytosis to be all or none. In contrast to the all or none hypothesis, here we discuss the evidence that during exocytosis the vesicle-membrane pore opens to release only a portion of the transmitter content during exocytosis and then close again. This open and closed exocytosis is distinct from kiss-and-run exocytosis, in that it appears to be the main content released during regular exocytosis. The evidence for this partial release via open and closed exocytosis is presented considering primarily the quantitative evidence obtained with amperometry.
2.2. The stellar content of the Quintuplet cluster
Authors: Figer Donald F. , McLean Ian S. , Morris Mark , Najarro Francisco 
Published: July 2016

The Quintuplet cluster contains over two dozen post main sequence descendants of massive O-stars, including Wolf-Rayet and OBI stars.The five Quintuplet-proper members (QPMs) may be dusty late-type Wolf-Rayet carbon stars (DWCLs), and the Pistol star may have a very high luminosity, ≈ 106.7±0.5 L⊙. Coupled with its rather cool temperature, 12–23 kK, the Pistol Star is well in violation of the Humphreys–Davidson limit. We argue that the surrounding “Pistol” nebula was ejected from the star a few thousand years ago.The cluster stars imply the following approximate cluster properties: tage ∼ 2 to 7 Myrs, M ∼ 104 M⊙, L ∼ 107.3±0.2 L⊙, and NLy,c > 1049.9 s−1. The “Sickle” (G0.18–0.04) radio feature and the mid-IR ring (seen in MSX images) may naturally be explained by the presence of a young cluster and a nearby molecular cloud.
3.19. ROSAT HRI observations of the young starburst galaxy NGC 5253
Authors: Strickland D. K. , Stevens I. R. 
Published: July 2016

Large numbers of Wolf-Rayet stars in the nearby (4.1 Mpc) star-bursting dwarf galaxy NGC 5253 indicate the starburst is only ~ 5 million years old (Schaerer et al. 1997). This makes NGC 5253 an ideal object for studying the early phases of starburst activity, in particular superbubbles blown by supernovae and winds from massive stars.Previous low resolution observations suggested the observed X-ray emission was due to a superbubble. We use the enhanced resolution available with a long ROSAT High Resolution Imager (HRI) observation and find that the X-ray emission arises from several unresolved sources associated with the young star clusters seen in the optical. We discuss the possible origins of the point-like emission, and find that they could be small superbubbles blown by the individual clusters of massive stars.
Galaxy Formation: ISOCAM Counts
Authors: Cesarsky C.J. , Elbaz D. 
Published: July 2016

Detailed observations in the optical do not allow to discriminate between the following scenarii of galaxy formation:- synchronous formation at large redshift (z &gt; 7).- hierarchical merging, down to z ≤ 1, of proto-galactic lumps formed at very high redshift (≈ 10).- galaxy formation at low z (≈ 2-5), but partially obscured by dust.More than 1500 galaxies in a field of 2.6′ × 4.6′ were detected by Tyson (1988) with CCD images in the B band. These deep counts of galaxies revealed the presence of an unexpectedly large population of blue galaxies, corresponding to a number excess of 3 to 5 times more galaxies at B &gt; 23 than one can expect from the local luminosity function. These objects lie apparently at moderate redshift (z = 0.3 for B = 23–24) as shown by spectroscopy of B-selected galaxies (Collesset al.1990).
The Cosmological Diffuse γ-Ray Background: Myth or Reality?
Authors: Laurent P. 
Published: July 2016

This paper is by no means a critical review of what have been thought, calculated or written about the cosmological diffuse γ-ray background. More simply, it is intended to tell its story, in order to answer a may be more historical than astronomical question:“How ideas about the cosmological diffuse γ-ray background has evolved since the beginning of the space era ?”
Powerful Extended Radio Sources: A Goldmine for Cosmology
Authors: Daly R. A. 
Published: July 2016

The radio properties of powerful extended radio sources may be used to study the environments of the sources, the source energetics, a characteristic length-scale that can be used as a cosmological tool, and the relation between radio galaxies and radio loud quasars. Thus, these sources offer a rich variety of diagnostics, both direct and indirect, of the cosmological model that describes our universe. They, indeed, are a goldmine for cosmology.Perhaps the most significant result of the investigations mentioned here is the use of the radio properties of the sources to estimate the ambient gas density in the vicinity of the radio lobe. As discussed below, the ambient gas densities estimated using the strong shock jump conditions across the radio lobe indicate that these sources lie in relatively dense gaseous environments, similar to the intracluster medium found in clusters of galaxies at low redshift. Thus, the observations suggest that at least some clusters with their intracluster medium in place exist at high redshift.
CDS UV Brightenings Explained by Quasi-separatrices and Bald Patches in an S-shape Active Region
Authors: Schmieder B. , Démoulin P. , Fletcher L. , López Fuentes M. C. , Mandrini C. H. , Mason H. E. , Young P. R. , Nitta N. 
Published: July 2016

We present multi-instrument observations of AR 8048, made between June 3 and June 5 1997 as part of SoHO JOP033. This active region (AR) has a sigmoid-like global shape and undergoes transient brightenings through which the stored energy is released.Using a magneto-hydrostatic model, we compute coronal magnetic field. The large-scale magnetic lines confirm the sigmoidal characteristics of the AR. The field lines most closely matching the hotter SoHO/CDS loops extend along the quasi-separatrix-Iayers (QSLs) of the coronal field. Transition region (TR) brightenings observed with SoHO/CDS can be associated with both QSL intersections with the photosphere, and places where separatrices corresponding to bald patches (BPs, sites where field lines are tangent to the photosphere) lie at the photospheric plane. There are suggestions that the element abundances measured in the TR may depend on the type of topological structure present. TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values.
Should the Outer Milky Way be Axisymmetric?
Authors: Binney James 
Published: July 2016

The shape of the outer Milky Way should be heavily influenced by the shape of our heavy halo. Simulations of the formation of collisionless halos indicate that they should be highly triaxial, with a tendency to pro-lateness. If our halo were as strongly triaxial as these simulations suggest, the outer disk would have ellipticity ϵdisk ≃ 0.06.Simulations of galaxy formation which include an appropriately small fraction of gaseous matter give rise to halos of much smaller ellipticity, and predict ϵdisk ≃ 0.02. These simulations are not as reliable as purely collisionless simulations, and we should treat their results with some caution. However, it is not incredible that a small fraction of gas could radically reduce the ellipticity of a halo by making the system's potential more centrally concentrated.The distribution of the apparent ellipticities of spiral galaxies indicates that their disks have slightly eliptical disks, ϵdisk ≃ 0.05. This may merely reflect ephemeral features such as spiral arms, however. The velocity fields of disks provide a more robust probe of the ellipticity ϵΦ of galaxy potentials. The narrowness of the Tully–Fisher relation places an interesting upper limit ϵΦ < 0.1. More detailed studies of individual velocity fields will be required if we are unambiguously to demonstrate ϵΦ > 0 in some cases.
The Structure of the Neutral Interstellar Medium: A Theory of Interstellar Turbulence
Authors: Whitworth Anthony 
Published: July 2016

We present a model for the development of density structure in the neutral interstellar medium. In this model, bulk kinetic energy is injected mainly at small scales, by jets and expanding nebulae generated by young and/or massive stars. Subsequently, this bulk kinetic energy propagates to, and is dissipated on, larger scales.This is in contrast to standard (incompressible) Kolmogorov turbulence, where kinetic energy is injected at larger scales, then propagates to, and is dissipated on, smaller scales. The sense in which the Second Law of Thermodynamics drives the propagation of turbulent energy is reversed in the interstellar medium because virialized self-gravitating gas clumps and ensembles of clumps (clouds) have negative effective specific heat.The model is able to explain Larson's relations (between the mass, size, and velocity-dispersion of molecular clouds and clumps; Larson 1981), the maximum masses of giant molecular cloud complexes, the velocity dispersions observed (at low resolution) in face-on spirals like the Milky Way, and the apparent scaling of the interstellar magnetic field with density.