NASTRAN flutter analysis of advanced turbopropellers

An existing capability developed to conduct modal flutter analysis of tuned bladed-shrouded discs in NASTRAN was modified and applied to investigate the subsonic unstalled flutter characteristics of advanced turbopropellers. The modifications pertain to the inclusion of oscillatory modal aerodynamic loads of blades with large (backward and forward) variable sweep. The two dimensional subsonic cascade unsteady aerodynamic theory was applied in a strip theory manner with appropriate modifications for the sweep effects. Each strip is associated with a chord selected normal to any spanwise reference curve such as the blade leading edge. The stability of three operating conditions of a 10-bladed propeller is analyzed. Each of these operating conditions is iterated once to determine the flutter boundary. A 5-bladed propeller is also analyzed at one operating condition to investigate stability. Analytical results obtained are in very good agreement with those from wind tunnel tests

Ephedrine requirements are reduced during spinal anaesthesia for caesarean section in preeclampsia

Part of the Portfolio Thesis by Geoffrey H. Sharwood-Smith: The inferior vena caval compression theory of hypotension in obstetric spinal anaesthesia: studies in normal and preeclamptic pregnancy, a literature review and revision of fundamental concepts, available at http://hdl.handle.net/10023/1815Background: Despite controversy over the haemodynamically safest blockade for caesarean section in women with severe preeclampsia, an increasing number of anaesthetists now opt for spinal anaesthesia. In a previous study we found that spinal compared to epidural anaesthesia offered an equally safe but more effective option for these patients. The current study was designed to compare the hypotension induced by spinal anaesthesia, as measured by ephedrine requirement, between 20 normotensive and 20 severely preeclamptic but haemodynamically stabilised women. Method: Standardised spinal anaesthesia was instituted and ephedrine was given in boluses of 6 mg if the systolic pressure fell >20% from the baseline, or if the patient exhibited symptoms of hypotension. Results: The mean ephedrine requirement of the normotensive group (27.9 ± 11.6 mg) was significantly greater (P < 0.01) than that of the preeclamptic group (16.4 ± 15.0 mg). Conclusion: This suggests that the hypotension induced by spinal anaesthesia in women with severe but haemodynamically stabilised preeclampsia, is less than that of normotensive patients.Publisher PD

Finite element forced vibration analysis of rotating cyclic structures

A capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axes of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical development of this capability is presented

Nastran level 16 theoretical manual updates for aeroelastic analysis of bladed discs

A computer program based on state of the art compressor and structural technologies applied to bladed shrouded disc was developed and made operational in NASTRAN Level 16. Aeroelastic analyses, modes and flutter. Theoretical manual updates are included

An alternative method of analysis for base accelerated dynamic response in NASTRAN

An alternative method of analysis to determine the dynamic response of structures subjected to base accelerations is presented. The method is exact as opposed to the approximate technique of using unusually large masses and loads to enforce desired base accelerations. This paper presents the relevant equations to motion, ALTERs for direct and modal frequency-, random- and transient-response rigid formats, and illustrative examples

Threshold corrections to rapidity distributions of Z and W^\pm bosons beyond N^2 LO at hadron colliders

Threshold enhanced perturbative QCD corrections to rapidity distributions of $Z$ and $W^\pm$ bosons at hadron colliders are presented using the Sudakov resummed cross sections at N${}^3$LO level. We have used renormalisation group invariance and the mass factorisation theorem that these hard scattering cross sections satisfy to construct the QCD amplitudes. We show that these higher order threshold QCD corrections stabilise the theoretical predictions for vector boson production at the LHC under variations of both renormalisation and factorisation scales.Comment: 17 pages, 8 eps figures. This paper is dedicated to the memory of W.L.G.A.M. van Neerve

Acoustical modes of arbitrary volumes using NASTRAN transient heat transfer RF9

An equivalence between temperature and pressure, heat conduction and stiffness and heat capacity and mass is defined, enabling acoustical modal analysis of arbitrary three dimensional volumes. The transient heat transfer analysis rigid format in NASTRAN, RF9, has been altered providing the acoustical analysis capability. Examples and ALTERs are included

Surveyor landing radar test program review Final report

Test program evaluation and modifications for Surveyor radar altimeter and Doppler velocity sensor syste

Rapid modulation of sensory processing induced by stimulus conflict

Humans are constantly confronted with environmental stimuli that conflict with task goals and can interfere with successful behavior. Prevailing theories propose the existence of cognitive control mechanisms that can suppress the processing of conflicting input and enhance that of the relevant input. However, the temporal cascade of brain processes invoked in response to conflicting stimuli remains poorly understood. By examining evoked electrical brain responses in a novel, hemifield-specific, visual-flanker task, we demonstrate that task-irrelevant conflicting stimulus input is quickly detected in higher level executive regions while simultaneously inducing rapid, recurrent modulation of sensory processing in the visual cortex. Importantly, however, both of these effects are larger for individuals with greater incongruency-related RT slowing. The combination of neural activation patterns and behavioral interference effects suggest that this initial sensory modulation induced by conflicting stimulus inputs reflects performance-degrading attentional distraction because of their incompatibility rather than any rapid task-enhancing cognitive control mechanisms. The present findings thus provide neural evidence for a model in which attentional distraction is the key initial trigger for the temporal cascade of processes by which the human brain responds to conflicting stimulus input in the environment