Numerical Investigation of Optimal Pin Actuator Location on a Supersonic Projectile

The flowfield around a supersonic projectile using a pin actuator control method has been predicted using computational fluid dynamics. It has been predicted using both viscous and inviscid methods for a number of positions. Both methods showed that an optimal longitudinal position exists. However, the inviscid model over-predicted the lateral acceleration due to the difference in shock formation around the pin between the two approaches. The optimal location was predicted independent of solver, however the higher-fidelity solver predicted lower achievable lateral accelerations. This is due to the viscous interactions caused by the pin. The effect of projectile orientation has shown that shielding the pin leads to reduced effectiveness due to the wake of the fin enveloping the pin. When the pin is exposed to onset flow, the forces achieved are increased. There is also an increase in the achievable forces and moments with increasing Mach number.

Framework for Establishing Limits of Tabular Aerodynamic Models for Flight Dynamics Analysis

This paper describes the use of the Euler equations for the generation and testing of tabular aerodynamic models for flight dynamics analysis. Maneuvers for the AGARD Standard Dynamics Model sharp leading-edge wind-tunnel geometry are considered as a test case. Wind-tunnel data is first used to validate the prediction of static and dynamic coefficients at both low and high angles, featuring complex vortical flow, with good agreement obtained at low to moderate angles of attack. Then the generation of aerodynamic tables is described based on a data fusion approach. Time-optimal maneuvers are generated based on these tables, including level flight trim, pull-ups at constant and varying incidence, and level and 90 degrees turns. The maneuver definition includes the aircraft states and also the control deflections to achieve the motion. The main point of the paper is then to assess the validity of the aerodynamic tables which were used to define the maneuvers. This is done by replaying them, including the control surface motions, through the time accurate computational fluid dynamics code. The resulting forces and moments are compared with the tabular values to assess the presence of inadequately modeled dynamic or unsteady effects. The agreement between the tables and the replay is demonstrated for slow maneuvers. Increasing rate maneuvers show discrepancies which are ascribed to vortical flow hysteresis at the higher rate motions. The framework is suitable for application to more complex viscous flow models, and is powerful for the assessment of the validity of aerodynamics models of the type currently used for studies of flight dynamics.

Mesoscale flux-closure domain formation in single-crystal BaTiO3

Over 60 years ago, Charles Kittel predicted that quadrant domains should spontaneously form in small ferromagnetic platelets. He expected that the direction of magnetization within each quadrant should lie parallel to the platelet surface, minimizing demagnetizing fields, and that magnetic moments should be configured into an overall closed loop, or flux-closure arrangement. Although now a ubiquitous observation in ferromagnets, obvious flux-closure patterns have been somewhat elusive in ferroelectric materials. This is despite the analogous behaviour between these two ferroic subgroups and the recent prediction of dipole closure states by atomistic simulations research. Here we show Piezoresponse Force Microscopy images of mesoscopic dipole closure patterns in free-standing, single-crystal lamellae of BaTiO3. Formation of these patterns is a dynamical process resulting from system relaxation after the BaTiO3 has been poled with a uniform electric field. The flux-closure states are composed of shape conserving 90° stripe domains which minimize disclination stresses.

A Royal Encounter: space, spectacle and the Queen’s visit to Ireland 2011

This commentary reflects on the first official visit made by a British monarch to Ireland since its independence. Focusing on three key moments of Queen Elizabeth's itinerary – the Garden of Remembrance, the Irish National War Memorial, Islandbridge, and the state banquet, Dublin Castle – I suggest that efforts to simultaneously honour rebels/soldiers in acts of public remembrance sought to re-position the past between these two islands in ways which recognised conflict but also aspired towards reconciled understandings of how that past could be more peacefully calibrated.

The UMIST database for astrochemistry 1995

We report the release of a new version of the UMIST database for astrochemistry. The database contains the rate coefficients of 3864 gas-phase reactions important in interstellar and circumstellar chemistry and involves 395 species and 12 elements. The previous (1990) version of this database has been widely used by modellers. In addition to the rate coefficients, we also tabulate permanent electric dipole moments of the neutral species and heats of formation. A numerical model of the chemical evolution of a dark cloud is calculated and important differences to that calculated with the previous database noted.

GAS-PHASE REACTIONS AND RATE COEFFICIENTS FOR USE IN ASTROCHEMISTRY - THE UMIST RATEFILE

We present the rate coefficients of 2880 gas-phase reactions among 313 species involving 12 elements for use in astrochemical models. We describe the motivation behind this work and the caveats which attach to the data in general as well as to specific reactions. We give the permanent electric dipole moments of nearly all the 112 neutral molecules contained in the data set, so that rate coefficients can be calculated at the low temperatures of dark interstellar dust clouds. We have used the data to calculate the pseudo-time-dependent chemical evolution of a dark, dense interstellar cloud and present both early time and steady-state abundances for all 313 species.

The comparative solvatochromism of arylazo and heteroarylazo compounds based on N,N-diethyl-m-acetylaminoaniline and N,N-diethyl-m-toluidine

Azobenzene dyes derived from various anilines and aminothiaheterocycles ate-coupled with commercially important N,N-diethyl-m-toluidine (T series) and iv,N-diethyl-m-acetylaminoaniline (A series) are positively solvatochromic. The visible spectra of 16 pairs of derivatives have been measured in up to 22 solvents, and the transition energies related to Kamlet-Taft solvent polarity parameters. In general, A-series dyes are more bathochromic than their T-series counterparts in nonpolar solvents, consistent with colour chemistry tradition, However, in more dipolar solvents the more bathochromic T-series representatives unexpectedly become more bathochromic than their A-series partners. The relative solvatochromic shifts of the A and T series are related to their respective dipole moments, These in turn are distinguished by the effect of the anilide carbonyl group dipole moment, which is antiparallel to, and thus reduces, the dipole moment of the chromogen.

Information disclosure and depositor discipline in the Chinese banking sector

We investigate the relationship between information disclosure and depositor behaviour in the Chinese banking sector. Specifically, we enquire whether enhanced information disclosure enables investors to more effectively infer a banking institution's risk profile, thereby influencing their deposit decisions. Utilising an unbalanced panel, incorporating financial data from 169 Chinese banks over the 1998–2009 period, we employ generalised-method-of-moments (GMM) estimation procedures to control for potential endogeneity, unobserved heterogeneity, and persistence in the dependent variable. We uncover evidence that: (i) the growth rate of deposits is sensitive to bank fundamentals after controlling for macroeconomic factors, diversity in ownership structure, and government intervention; (ii) a bank publicly disclosing more transparent information in its financial reports, is more likely to experience growth in its deposit base; and (iii) banks characterised by high information transparency, well-capitalised and adopted international accounting standards, are more able to attract funds by offering higher interest rates.

Design of composite asymmetric cellular beams and beams with large web openings

The design of composite asymmetric cellular beams is not fully covered by existing guidance but is an area of important practical application. Asymmetry in the shape of the cross-section of cellular beams causes development of additional bending moments in the web-posts between closely placed openings. Furthermore, the development of local composite action influences the distribution of forces in the web-flange Tees. The design method presented in this paper takes account of high degrees of asymmetry in the cross-section and also the influence of elongated or rectangular openings.

Random particle motion in magnetized plasma

A multivariate Fokker-Planck-type kinetic equation modeling a test - panicle weakly interacting with an electrostatic plasma. in the presence of a magnetic field B . is analytically solved in an Ornstein - Uhlenbeck - type approximation. A new set of analytic expressions are obtained for variable moments and panicle density as a function of time. The process is diffusive.

The machinist landscape:Land Art Generator Initiative (Competition)

THE MACHINIST LANDSCAPE: AN ENTROPIC GRID OF VARIANCE
‘By drawing a diagram, a ground plan of a house, a street plan to the location of a site, or a topographic map, one draws a “logical two dimensional picture”. A “logical picture” differs from a natural or realistic picture in that it rarely looks like the thing it stands for.’
A Provisional Theory of Non-Sites, Robert Smithson (1968)

Between design and ground there are variances, deviations and gaps. These exist as physical interstices between what is conceptualised and what is realised; and they reveal moments in the design process that resist the reconciliation of people and their environment (McHarg 1963). The Machinist Landscape interrogates the significance of these variances through the contrasting processes of coppice and photovoltaic energy. It builds on the potential of these gaps, and in doing so proposes that these spaces of variance can reveal the complexity of relationships between consumption and remediation, design and nature.
Fresh Kills Park, and in particular the draft master plan (2006), offers a framework to explore this artificial construct. Central to the Machinist Landscape is the analysis of the landfill gas collection system, planned on a notional 200ft grid. Variations are revealed between this diagrammatic grid measure and that which has been constructed on the site. These variances between the abstract and the real offer the Machinist Landscape a powerful space of enquiry. Are these gaps a result of unexpected conditions below ground, topographic nuances or natural phenomena? Does this space of difference, between what is planned and what is constructed, have the potential to redefine the dynamic processes and relations with the land?
The Machinist Landscape is structured through this space of variance with an ‘entropic grid’, the under-storey of which hosts a carefully managed system of short-rotation coppice (SRC). The coppice, a medieval practice related to energy, product, and space, operates on theoretical and programmatic levels. It is planted along a structure of linear bunds, stabilized through coppice pole retaining structures and enriched with nutrients from coppice produced bio-char. Above the coppice is built an upper-storey of photovoltaic (PV); its structures fabricated from the coppiced timber and the PV produced with graphene from coppice charcoal processes.

The Casual Buttress:Certainty and Contingency in the Study of the Vernacular

Impromptu accretions such as the buttresses in Robin Walkers photograph are moments that are familiar in the architecture of the everyday. Indeed the buttress is a very common occurrence with these cottages in particular, their mud walls being poor at resisting concentrated lateral loading. While not always required the buttress emerges when requirements to create spaces to support inhabitation are at odds with the external form and construction of the buildings. These points of disjunction are resolved in an additive fashion externally. The location varies from structure to structure, occasionally the buttress is be used as a point of connection for further structures, becoming subsumed in outbuildings or walls. This preponderance to variety means that it is omitted from the reductive drawings of type that classify these buildings and yet it occurs in enough for it to have a fundamental and transformative relationship to the generality of cottages.
What is of interest is not so much what these structures hold in common, but rather what differentiates them. It is their capacity for variety within a defined range which allows them at once to speak at once of broader social structures and of a specific place and person.
Using the above observation this paper treats of the failure of architectural typological studies of the vernacular to derive anything other than formal exemplars, and posits an alternative approach based on a focus on the technical construction of such buildings.

Stiffener debonding mechanisms in post-buckled CFRP aerospace panels

This paper describes the fractographic analysis of five CFRP post-buckled skin/stringer panels that were tested to failure in compression. The detailed damage mechanisms for skin/stiffener detachment in an undamaged panel were characterised and related to the stress conditions during post-buckling; in particular the sites of peak twist (at buckling nodes) and peak bending moments (at buckling anti-nodes). The initial event was intralaminar splitting of the +45 degrees plies adjacent to the skin/stiffener interface, induced by high twist at a nodeline. This was followed by mode II delamination, parallel to +/- 45 degrees plies and then lengthwise (0 degrees) shear along the stiffener centreline. The presence of defects or damage was found to influence this failure process, leading to a reduction in strength. This research provides an insight into the processes that control post-buckled performance of stiffened panels and suggests that 2D models and element tests do not capture the true physics of skin/stiffener detachment: a full 3D approach is required.

On the required shape corrections to the local density and generalized gradient approximations to the Kohn-Sham potentials for molecular response calculations of (hyper)polarizabilities and excitation energies

It is well known that shape corrections have to be applied to the local-density (LDA) and generalized gradient (GGA) approximations to the Kohn-Sham exchange-correlation potential in order to obtain reliable response properties in time dependent density functional theory calculations. Here we demonstrate that it is an oversimplified view that these shape corrections concern primarily the asymptotic part of the potential, and that they affect only Rydberg type transitions. The performance is assessed of two shape-corrected Kohn-Sham potentials, the gradient-regulated asymptotic connection procedure applied to the Becke-Perdew potential (BP-GRAC) and the statistical averaging of (model) orbital potentials (SAOP), versus LDA and GGA potentials, in molecular response calculations of the static average polarizability alpha, the Cauchy coefficient S-4, and the static average hyperpolarizability beta. The nature of the distortions of the LDA/GGA potentials is highlighted and it is shown that they introduce many spurious excited states at too low energy which may mix with valence excited states, resulting in wrong excited state compositions. They also lead to wrong oscillator strengths and thus to a wrong spectral structure of properties like the polarizability. LDA, Becke-Lee-Yang-Parr (BLYP), and Becke-Perdew (BP) characteristically underestimate contributions to alpha and S-4 from bound Rydberg-type states and overestimate those from the continuum. Cancellation of the errors in these contributions occasionally produces fortuitously good results. The distortions of the LDA, BLYP, and BP spectra are related to the deficiencies of the LDA/GGA potentials in both the bulk and outer molecular regions. In contrast, both SAOP and BP-GRAC potentials produce high quality polarizabilities for 21 molecules and also reliable Cauchy moments and hyperpolarizabilities for the selected molecules. The analysis for the N-2 molecule shows, that both SAOP and BP-GRAC yield reliable energies omega(i) and oscillator strengths f(i) of individual excitations, so that they reproduce well the spectral structure of alpha and S-4.(C) 2002 American Institute of Physics.

Chemical tuning of the interlayer magnetic coupling in TlCo2Se2-xSx

The system TlCo2Se2-xSx has been thoroughly investigated by neutron powder diffraction and SQUID magnetometry. TlCo2Se2-xSx is a layered tetragonal structure containing atomic cobalt layers separated by a distance of 6.4 angstrom in the sulphide and 6.8 angstrom in the selenide. The solid solubility of isovalent selenium and sulphur atoms in the structure makes it possible to continuously vary the interlayer distance and thereby tune the magnetic coupling between the Co-layers. At low temperatures, the Co-atoms are ferromagnetically ordered within the layers and magnetic moments lie in the ab-plane. However, these Co-moments form a helical magnetic structure that prevails for 0 <= x <= 1.5 with a gradual decrease of the angle between adjacent Co-layers from 122 degrees to 39 degrees. For x >= 1.75, a collinear ferromagnetic structure is stable. The relationship between the coupling angle and the Co-interlayer separation shows an almost linear behaviour. The helical phase contains no net spontaneous magnetic moment up to TlCo2SeS, where a small net magnetic moment appears that increases until the ferromagnetic structure is found for 1.75 <= x <= 2.0. (C) 2005 Elsevier B.V. All rights reserved.