4,095 research outputs found
A Wind Tunnel Simulation Facility for On-Road Transients
No full textThis paper outlines the creation of a facility for simulating on-road transients in a model scale, ¾ open jet, wind tunnel.
Aerodynamic transients experienced on-road can be important in relation to a number of attributes including vehicle handling and aeroacoustics. The objective is to develop vehicles which are robust to the range of conditions that they will experience. In general it is cross wind transients that are of greatest significance for road vehicles. On-road transients include a range of length scales but the most important scales are in the in the 2-20 vehicle length range where there are significant levels of unsteadiness experienced, the admittance is likely to be high, and the reduced frequencies are in a band where a dynamic test is required to correctly determine vehicle response.
Based on measurements of on-road conditions, the aim was for the turbulence generation system to achieve yaw angles up to 6-8°, equating to a lateral turbulence intensity of 8-10% with a frequency range extending up to 10 Hz. In a wind tunnel, the generation of scales larger than the scale of the vehicle is impractical with passive grids and so an active turbulence generation system is required. The system includes a pair of vertical airfoils at the upstream end of the test section. The yawing of the wind tunnel jet requires correct handling at the downstream end of the test section and hence additional outlets were incorporated with cascading shutters to control collector width and effective location. Similarly, additional, shuttered, inlets were incorporated at the upstream end of the test section. The maximum steady state yaw angle range achieved was ±8° steady state, extending to ±11° in dynamic operation. The turbulence generation system can be programmed to reproduce specific events as measured on-road, with time appropriately scaled for model testing.
Tests with a vehicle model validated that the turbulence generation system operating in a steady state mode results in the same steady forces as achieved yawing the model on a turntable. The system's ability to model specific on-road conditions was also demonstrated
Gluon and quark propagators in Landau gauge from the lattice
No full textA.G. Williams, P.O. Bowman, F.D.R. Bonnet, D.B. Leinweber, and J.-I. Skulleru
Hadron properties with FLIC fermions
No full textThe Fat-Link Irrelevant Clover (FLIC) fermion action provides a new form of
nonperturbative O(a)-improvement in lattice fermion actions offering near
continuum results at finite lattice spacing. It provides computationally
inexpensive access to the light quark mass regime of QCD where chiral
nonanalytic behaviour associated with Goldstone bosons is revealed. The
motivation and formulation of FLIC fermions, its excellent scaling properties
and its low-lying hadron mass phenomenology are presented.J.M. Zanotti, D.B. Leinweber, W. Melnitchouk, A.G. Williams and J.B. Zhan
Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant
No full textOn-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. Separated flow structures in the sideglass region of a vehicle are particularly sensitive to unsteadiness in the onset flow. These regions are also areas where strong aeroacoustic effects can exist, in a region close to the passengers of a vehicle. The resulting aeroacoustic response to unsteadiness can lead to fluctuations and modulation at frequencies that a passenger is particularly sensitive towards. Results presented by this paper combine on-road measurement campaigns using instrumented vehicles in a range of different wind environments and aeroacoustic wind tunnel tests.
A new cabin noise simulation technique was developed to predict the time-varying wind noise in a vehicle using the cabin noise measured in the steady environment of the wind tunnel, and a record of the unsteady onset conditions on the road, considering each third-octave band individually. The simulated cabin noise predicted using this quasi-steady technique was compared against direct on-road cabin noise measurements recorded under the same flow conditions to assess the response of the vehicle to oncoming flow unsteadiness.
The technique predicted the modulation of the wind noise under unsteady on-road conditions with good fidelity. This is because the cabin noise response to oncoming flow unsteadiness remained generally quasi-steady up to fluctuation frequencies of approximately 2 to 5 Hz, with fluctuations at higher scales having a progressively smaller impact, and because most of the onset flow fluctuation energy on the road occurs at frequencies below this threshold.
The relative impact of the baseline level of cabin noise and the sensitivity of the cabin noise to changes in yaw angle were assessed in terms of occupant perception and this highlighted the importance of modulation. This can provide guidance when assessing the on-road wind noise performance of vehicle geometry modifications and of different vehicles
Williams College : order of exercises for the induction of Harry Augustus Garfield, LL.D. into the office of President, October seventh MDCCCCVIII.
No full textCover-title: Williams College, induction of the president, MDCCCCVIII.Smith, J.P. Merrymount Press (1975),Mode of access: Internet
Dr D.B. Smuts : Onderstepoort staff
No full textScanned image of a photographic glass-plate negativeDr D.B. Smuts, Onderstepoort staff memberin the Section of Nutrition in the late 1930's. He was co-author of the article "The Nutritive Value of Animal Proteins.-
The Biological Values of Fishmeal, Whale and Fishmeal, Meatmeal, Meat and Bonemeal, Crayfishmeal, and White Fishmeal" published in the Onderstepoort Journal of Veterinary Science and Animal Industry, Volume 16, Numbers 1 and 2, January and April, 1941.Digitised by the Department of Library Services, University of Pretoria, 2019ab201
VPD/SIMS Measurement of Surface Al on Silicon Substrates
No full textABSTRACTAn experimental protocol using secondary ion mass spectrometry to measure Al in vapor phase decomposition (VPD) solutions has been developed to achieve a detection limit of 108 atoms/cm2. The analytical technique is called VPD/SIMS. The procedure utilizes sample preparation techniques developed for microvolume SIMS. Preliminary SIMS analysis of simulated VPD solutions consisting of dilute HF indicate that a theoretical detection limit of 5.7×105 Al atoms/cm2 is possible from a 6″ wafer.</jats:p
Visually guided step descent in children with Williams syndrome
No full textIndividuals with Williams syndrome (WS) have impairments in visuospatial tasks and in manual visuomotor control, consistent with parietal and cerebellar abnormalities. Here we examined whether individuals with WS also have difficulties in visually controlling whole-body movements. We investigated visual control of stepping down at a change of level in children with WS (5–16-year-olds), who descended a single step while their movement was kinematically recorded. On each trial step height was set unpredictably, so that visual information was necessary to perceive the step depth and position the legs appropriately before landing. Kinematic measures established that children with WS did not use visual information to slow the leg at an appropriate point during the step. This pattern contrasts with that observed in typically developing 3- and 4-year-old children, implying severe impairment in whole-body visuomotor control in WS. For children with WS, performance was not significantly predicted by lowlevel visual or balance problems, but improved significantly with verbal age. The results suggest some plasticity and development in WS whole-body control. These data clearly show that visuospatial and visuomotor deficits in WS extend to the locomotor domain. Taken together with evidence for parietal and cerebellar abnormalities in WS, these results also provide new evidence for the role of these circuits in the visual control of whole-body movement
Letter, 1858 May 8, D.B. Sanchez (?) to Henry Honaker
No full textLetter regarding the sale of a bull. Last name of author unclear, possibly Sanchez or San..z
Cross Winds and Transients: Reality, Simulation and Effects
No full textThis paper provides a published counterpart to the address of the same title at the 2010 SAE World Congress. A vehicle on the road encounters an unsteady flow due to turbulence in the natural wind, due to the unsteady wakes of other vehicles and as a result of traversing through the stationary wakes of road side obstacles. This last term is of greatest significance. Various works related to the characterization, simulation and effects of on-road turbulence are compared together on the turbulence spectrum to highlight differences and similarities. The different works involve different geometries and different approaches to simulating cross wind transients but together these works provide guidance on the most important aspects of the unsteadiness. On-road transients include a range of length scales spanning several orders of magnitude but the most important scales are in the in the 2-20 vehicle length range. There are significant levels of unsteadiness experienced on-road in this region and the corresponding frequencies are high enough that a dynamic test is required to correctly determine the vehicle response. Fluctuations at these scales generate significant unsteady loads (aerodynamic admittance typically 0.6-1.4) and the corresponding frequencies can adversely affect vehicle dynamics. The generation of scales larger than the scale of the vehicle is impractical with passive grids and so active turbulence generation systems are preferred. These can be classified into lift and drag-based devices. Lift-based devices provide better control of the turbulence but can only just reproduce the smaller scales in the 2-20 vehicle length range. Different moving model approaches are also discussed. CFD offers real advantages through its ability to allow arbitrary time-varying boundary conditions
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