2,017 research outputs found
A Parametric Study of Vane and Air-jet Vortex Generators
No full textAn experimental parametric sturdy of vane and air-jet vortex generators in a turbulent boundary
layer has been carried out. Experiments were carried out in two facilities, one with a free-stream
velocity of 20 m/s and a boundary layer thickness (6) of 41.5 mm, and one in a high speed facility
at free-stream Mach numbers of between 0.45 and 0.75 and a boundary layer thickness of 20 mm.
Cross-stream data were measured at a number of downstream locations using a miniature five-hole
pressure probe, such that local cross-stream velocity vectors could be derived. Streamwise
vorticity was calculated using the velocity vector data.
In the low speed study, vortex generator parameters were as follows:
" Vane vortex generators: thin rectangular vanes with a vane aspect ratio of unity (2h/c = 1),
free-stream velocity 20 m/s, incidence (cc = 10', 15', 18', 20'), height-to-boundary- layer-
thickness-ratio (h/8 0.554,0.916,1.27,1.639), and strearnwise distance from the vortex
generator (x/6 = 3.855,12.048,19.277,26.506).
" Air-jet vortex generators: circular jet nozzles, free-stream velocity = 20 m/s, jet nozzle pitch
and skew angles (cc, P= 30', 45', 60'), hole diameter-to-boundary-layer-thickness-ratio (D/5 =
0.098,0.193,0.289), jet-to-free-stream-velocity ratio (VR = 0.7,1.0,1.3,1.6,2.0), and
strearnwise distance from the vortex generator (x/8 = 3.855,12.048,19.277,26.506).
In the high-speed study, the vortex generator parameters were as follows:
Vane vortex generators: thin rectangular vanes with an aspect ratio of unity, incidence ((X
1505 20'), he i ght-to- boundary- I ayer-th i ckne s s-rati o (h/8 = 0.75), strearnwise distance from the
vortex generator (x/6 = 8.755 16.25,23.75), and free-stream Mach numbers of 0.45,0.6 and
0.75.
Air-jet vortex generators: jet pitch ((x = 30', 45'), jet skew angle (P = 30', 45', 60'), hole
diameter-to-boundary-layer-thickness-ratio (D/8 = 0.15,0.3), j et-to- free- strearn-ve loc ity ratio
(VR = 1.6), and strearnwise distance from the vortex generator (x/6 = 8.75,16.25,23.75,
31.25), and free-stream Mach numbers of 0.50,0.6 and 0.75.
Streamwise vorticity data from the experiment was used to generate prediction techniques that
would allow the vorticity profiles, downstream of vane or air-jet vortex generators, to be predicted.
Both techniques are based on the approximation of the experimental cross-stream vorticity data to
Gaussian distributions of vorticity through the vortex centre. The techniques, which are
empirically derived, are simple equations that give the peak vorticity and vortex radius based on
the vortex generator parameters. Use of these descriptors allows the assembly of the Gaussian
vorticity equation.
Both techniques are compared with the experimental data set and were seen to produce peak
vorticity results to within 12% and 20% (for the vanes and air-jets respectively), 15% for the
radius of the vortex, and 15% and 20% in vortex circulation (for the vanes and air-jets
respectively). The two simple prediction techniques allow good prediction of the vortex structure
at extremely low computational effort
Investigation into aero-hydrodynamic surfaces for wing-in-ground effect vehicle design.
No full textGarry, Kevin P. - Associate SupervisorThis project focuses on developing the required knowledge and engineering data to be
applied in the preliminary design of a Wing-in-Ground Effect vehicle.
Three concurrent work programmes are carried out, covering experimental testing of a
novel hull design, computational analysis of three wing profiles operating in ground
effect, and an experimental programme to validate an unusual profile using an
unconventional technique.
This work is intended to produce a reliable database of 2D aerodynamic coefficients by
establishing a robust methodology for numerical solution. A detailed range of heights
above ground and angles of attack have been included, and the methodology can be easily
applied to additional profiles in the future.
A model wing was constructed and towed near the bottom of a water tank to replicate the
physics and flow patterns of a wing immersed in an incompressible fluid moving over
static ground. The selected profile was included in the computational work and the results
of the two methods were compared.
A hull model was designed and built, then towed at high speed to assess its potential
performance in the take-off phase of WIG operation. As a radiussed-chined slender hull,
it would also be suitable for waterborne operation at modest speed, leading to the
possibility for a dual-purpose vehicle comfortable in air or water.
Finally, a parametric geometry tool was developed to explore the design space and assess
feasibility of various configurations. Relationships between primary components have
been derived to allow sizing and positioning with corresponding powering estimates, to
generate WIG conceptual designs.PhD in Energy and Powe
Science Fiction Collections in ARL Academic Libraries
No full textThis study assesses the extent to which ARL academic libraries collect science fiction novels. A core list of 200 novels, published between 1950 and 2000, that have either won science fiction awards or been cited on “best” lists were checked against the holdings of 112 ARL libraries. Findings suggest that science fiction is not extensively collected at most libraries studied. The study also assesses differences in how novels are collected by date and by nationality and gender of author. To support in-depth and serious research in a field of increasing scholarly interest, libraries may need to reconsider their collecting practices.The published version of this article appears in College & Research Libraries, and is available at this location: crl.acrl.org/content/67/1/15.full.pdfPeer reviewe
Polymer based immune modulation for the generation of an anti-tumor immune response
No full textIncreasing emphasis is being placed on overcoming tumor-associate immune escape mechanisms that facilitate disease progression. Understanding this immune tolerance and developing methods to overcome it provide advanced understanding to further develop vaccine strategies. In the current work we have engineered a polymer based therapy that enhances cellular immunity capable of generating anti-tumor activity. We have determined that a poly(lactic-co-glycolic acid) (PLGA) based delivery system encapsulating tumor associated antigen (ovalbumin, OVA) and the TLR9 agonist CpG motif DNA can initiate an effective type 1 mediated response. Local administration of the polymer therapy on E.G7-OVA lymphoma bearing mice significantly delayed tumor progression by eliciting a strong local and systemic IFN-γ mediated anti-tumor response. It was found that this response worked independently of antigen specific CTLs, which were active in the tumor draining lymph nodes yet incapable of retarding tumor formation. In analyzing the dendritic cell response to this polymer system, it was demonstrated that this delivery system indeed increased the Th1 phenotype of dendritic cells as measured by an increase in cell surface expression of CD80, CD86 and MHCII and secretion of the cytokines IL-12 and IFN-γ. In addition, introducing the immune modulator 1-Methyl Tryptophan (1-MT) in concert with the antigen and adjuvant enhanced the dendritic cell Th1 profile when delivered via the PLGA vesicle. Taken together, these studies demonstrate the immunological mechanisms and benefits of a PLGA based delivery system.Ph. D.Includes bibliographical referencesby Kevin P. Nikitczu
sj-pdf-1-car-10.1177_19476035211042406 – Supplemental material for Open Source Software for Automatic Subregional Assessment of Knee Cartilage Degradation Using Quantitative T2 Relaxometry and Deep Learning
No full textSupplemental material, sj-pdf-1-car-10.1177_19476035211042406 for Open Source Software for Automatic Subregional Assessment of Knee Cartilage Degradation Using Quantitative T2 Relaxometry and Deep Learning by Kevin A. Thomas, Dominik Krzemiński, Łukasz Kidziński, Rohan Paul, Elka B. Rubin, Eni Halilaj, Marianne S. Black, Akshay Chaudhari, Garry E. Gold and Scott L. Delp in CARTILAGE</p
Explaining Myanmar's Regime Transition: The Periphery is Central
No full textIn 2010, Myanmar (Burma) held its first elections after 22 years of direct military rule. Few compelling explanations for this regime transition have emerged. This article critiques popular accounts and potential explanations generated by theories of authoritarian ‘regime breakdown’ and ‘regime maintenance’. It returns instead to the classical literature on military intervention and withdrawal. Military regimes, when not terminated by internal factionalism or external unrest, typically liberalise once they feel they have sufficiently addressed the crises that prompted their seizure of power. This was the case in Myanmar. The military intervened for fear that political unrest and ethnic-minority separatist insurgencies would destroy Myanmar’s always-fragile territorial integrity and sovereignty. Far from suddenly liberalising in 2010, the regime sought to create a ‘disciplined democracy’ to safeguard its preferred social and political order twice before, but was thwarted by societal opposition. Its success in 2010 stemmed from a strategy of coercive state-building and economic incorporation via ‘ceasefire capitalism’, which weakened and co-opted much of the opposition. Having altered the balance of forces in its favour, the regime felt sufficiently confident to impose its preferred settlement. However, the transition neither reflected total ‘victory’ for the military nor secured a genuine or lasting peace
Productivity in Higher Education/ Kevin Stange, Kevin Strange, Caroline M. Hoxby.
No full textIn English.How do the benefits of higher education compare with its costs, and how does this comparison vary across individuals and institutions? These questions are fundamental to quantifying the productivity of the education sector. The studies in Productivity in Higher Education use rich and novel administrative data, modern econometric methods, and careful institutional analysis to explore productivity issues. The authors examine the returns to undergraduate education, differences in costs by major, the productivity of for-profit schools, the productivity of various types of faculty and of outcomes, the effects of online education on the higher education market, and the ways in which the productivity of different institutions responds to market forces. The analyses recognize five key challenges to assessing productivity in higher education: the potential for multiple student outcomes in terms of skills, earnings, invention, and employment; the fact that colleges and universities are "multiproduct" firms that conduct varied activities across many domains; the fact that students select which school to attend based in part on their aptitude; the difficulty of attributing outcomes to individual institutions when students attend more than one; and the possibility that some of the benefits of higher education may arise from the system as a whole rather than from a single institution. The findings and the approaches illustrated can facilitate decision-making processes in higher education.Hoxby, Caroline M. / Stange, Kevin -- Staiger, Douglas -- Hoxby, Caroline M. -- Minaya, Veronica / Scott-Clayton, Judith -- Riehl, Evan / Saavedra, Juan E. / Urquiola, Miguel -- Altonji, Joseph G. / Zimmerman, Seth D. -- Courant, Paul N. / Turner, Sarah -- Vlieger, Pieter De / Jacob, Brian / Stange, Kevin -- Deming, David J. / Lovenheim, Michael / Patterson, Richard -- Carrell, Scott E. / Kurlaender, Michal -- Frontmatter -- Contents -- Acknowledgments -- Introduction / 1. What Health Care Teaches Us about Measuring Productivity in Higher Education / 2. The Productivity of US Postsecondary Institutions / 3. Labor Market Outcomes and Postsecondary Accountability: Are Imperfect Metrics Better Than None? / 4. Learning and Earning: An Approximation to College Value Added in Two Dimensions / 5. The Costs of and Net Returns to College Major / 6. Faculty Deployment in Research Universities / 7. Measuring Instructor Effectiveness in Higher Education / 8. The Competitive Effects of Online Education / 9. Estimating the Productivity of Community Colleges in Paving the Road to Four- Year College Success / Contributors -- Author Index -- Subject Index1 online resource (392 p.)
Music for classical guitar by South African composers : a historical survey, notes on selected works and a general catalogue
No full textIncludes abstract.Includes bibliographical references (leaves 296-309).This is the first comprehensive investigation of music for, or including, the classical guitar by South African composers. The focus of this research has been, firstly, to uncover as much of the repertoire as possible, and, secondly, to collate, study, catalogue and report on the information. A brief historical survey of the guitar in South Africa provides the context within which this study was conducted. The primary sources of quantitative data collection were through the archival catalogues of the South African Music Rights Organisation and through personal contact with guitarists, composers and guitar teachers. Other sources consulted were publishers, broadcasting corporations, recording companies, libraries and the internet. The body of the dissertation comprises biographical sketches, background notes, analyses and technical notes on 17 selected solo and chamber works dating from 1947 to 2007 by some of South Africa's most prominent composers and guitaristcomposers. The repertoire ranges in style from the traditional and ethnically inspired to the experimental and abstract. As this is an empirical survey, each selected entry includes details on instrumentation, duration, level of difficulty, number of pages, scordatura, commissions or requests, sources or publishers, premières and recordings. A biography of each composer is provided as well as background notes which offer an overview of the selected work. The notes discuss historical, cultural, musical and extra-musical influences, and frequently include references to interview material. The commentaries on the selected works, with musical examples, include an analytical component describing structure, form, stylistic and compositional elements, while the technical observations include performance suggestions and a grading for each work
Wind Tunnel Modelling of Aerodynamic Baffle Arrays for Aircraft Exhaust Plume Control
No full textLocal air quality is one of the factors constraining the development of airports. In
countries of the European Union where new, stricter regulations for emissions of
nitrogen oxides (NOx) have been introduced since 2010, the limits of mean annual
concentrations are already exceeded at certain ground monitoring locations of large
airports. This research project investigates the possibility of abating the aircraft exhaust
plume at take-off by placing an array of aerodynamic windbreaks (‘baffles’) in the
runway end safety area close to the aircraft starting position.
The undertaken experimental investigation comprised sub-scale wind tunnel tests
and full-scale field trials with a BAe 146-301 aircraft, performing take-off and landing
cycles at Cranfield Airport. The initial wind tunnel experiments investigated the effect
of a solid baffle row, placed in the path of a buoyant nozzle jet, on the development of
the plume downstream. Using flow visualisation, the positive effect of the baffle row of
promoting buoyant rise of the plume away from the ground was demonstrated
successfully without the presence of wind tunnel flow. The investigation highlighted the
importance of the distance of the baffles relative to the jet source on their effectiveness.
In the presence of wind tunnel flow, the baffles caused an increased vertical spread of
the plume downstream, but the plume was not observed to separate from the ground.
In preparation of the field trials, the spatial arrangement of the baffle array was
investigated by means of wind tunnel drag measurements, performed with a skinfriction
balance. The experiments focused on key parameters such as the baffle slope
angle and row spacing, favouring a configuration of three rows of baffles of increasing
height. Based on the wind tunnel measurements, full-scale baffle prototypes were
designed and manufactured at Cranfield University and were deployed in the field trials.
Lidar and point sampler measurements during the field trials suggested that the
plume had risen away from the ground on one occasion when the aircraft was located
close to the baffles. A positive effect was shown in terms of reduced concentrations
downstream of the baffles. This result was not replicated when the aircraft was further
away from the baffles.
The subsequent wind tunnel experiments focused on replicating the field trials at
1:200 scale in Cranfield’s Atmospheric Boundary Layer Wind Tunnel. The aircraft was
represented at sub scale with a single stationary nozzle while the jet speed and buoyancy
were modelled using similarity parameters such as the Froude number and the ratio of
ambient and jet density. Mean concentration measurements were performed using a
Flame Ionisation Detector method releasing methane as tracer gas. The effect of the
baffles was observed to be mainly local in terms of reduced concentrations close the
ground due to their sheltering effect. A more prolonged effect was found to be the increase of the plume’s vertical spread resulting in an increase in mean concentrations
away from the ground
Fixing Australia’s incredible defence policy
No full textAustralia’s new government must make tough decisions in defence policy. Australia’s broad national interests and the challenging strategic environment in Indo-Pacific Asia make it essential to modernise the Australian Defence Force. The nation’s defence capabilities remain underfunded and its strategic edge in the region is eroding. The gap between the nation’s interests and capabilities is widening, and it is getting harder to meet the demands of the US alliance. Australia’s new government needs to restore focus and funding to defence.Key findings: The Australian government will need a first-principles review to identify the military strategy and force structure required to protect and advance the nation’s interests. The Australian government must increase defence funding in order to modernise the Australian Defence Force\u27s capabilities. Otherwise it will need to make drastic cuts to planned defence capability. The government must also think deeply about the role of the US alliance in Australia\u27s security, and take the initiative in shaping that alliance in Australia’s interests
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