1,002 research outputs found
Theoretical prediction of airplane stability derivatives at subcritical speeds
The theoretical development and application is described of an analysis for predicting the major static and rotary stability derivatives for a complete airplane. The analysis utilizes potential flow theory to compute the surface flow fields and pressures on any configuration that can be synthesized from arbitrary lifting bodies and nonplanar thick lifting panels. The pressures are integrated to obtain section and total configuration loads and moments due side slip, angle of attack, pitching motion, rolling motion, yawing motion, and control surface deflection. Subcritical compressibility is accounted for by means of the Gothert similarity rule
Military Versus Civilian Air Cargo Training for Hazardous Material
This paper addressed differences in the way air cargo handlers are trained in the military and civilian sectors. The paper reviewed the training process and determined which provided the most knowledgeable graduates. A brief review of the history of hazardous material accidents and incidents was presented to demonstrate the need for continuous and effective training. The main body of the paper addressed current directives and the current status of the industry. The researchers collected information from military and civilians who were actively involved in the air transportation of hazardous materials. These data were then used to test specific hypotheses concerning which group was more knowledgeable and therefore, received the best training. The researchers found that there were generally no occurrences in the overall knowledge level of the military and civilians tested concerning the air transport of hazardous materials. However, there were statistically significant differences found between the two different kinds of civilian carriers. There were also significant differences between military and civilian HAZMAT specialists when the individual\u27s number of years of experience was taken into consideration
Defect turbulence in inclined layer convection
We report experimental results on the defect turbulent state of undulation
chaos in inclined layer convection of a fluid withPrandtl number .
By measuring defect density and undulation wavenumber, we find that the onset
of undulation chaos coincides with the theoretically predicted onset for
stable, stationary undulations. At stronger driving, we observe a competition
between ordered undulations and undulation chaos, suggesting bistability
between a fixed-point attractor and spatiotemporal chaos. In the defect
turbulent regime, we measured the defect creation, annihilation, entering,
leaving, and rates. We show that entering and leaving rates through boundaries
must be considered in order to describe the observed statistics. We derive a
universal probability distribution function which agrees with the experimental
findings.Comment: 4 pages, 5 figure
Fractal Stability Border in Plane Couette Flow
We study the dynamics of localised perturbations in plane Couette flow with
periodic lateral boundary conditions. For small Reynolds number and small
amplitude of the initial state the perturbation decays on a viscous time scale
. For Reynolds number larger than about 200, chaotic transients
appear with life times longer than the viscous one. Depending on the type of
the perturbation isolated initial conditions with infinite life time appear for
Reynolds numbers larger than about 270--320. In this third regime, the life
time as a function of Reynolds number and amplitude is fractal. These results
suggest that in the transition region the turbulent dynamics is characterised
by a chaotic repeller rather than an attractor.Comment: 4 pages, Latex, 4 eps-figures, submitted to Phys. Rev. Le
Wavy stripes and squares in zero P number convection
A simple model to explain numerically observed behaviour of chaotically
varying stripes and square patterns in zero Prandtl number convection in
Boussinesq fluid is presented. The nonlinear interaction of mutually
perpendicular sets of wavy rolls, via higher mode, may lead to a competition
between the two sets of wavy rolls. The appearance of square patterns is due to
the secondary forward Hopf bifurcation of a set of wavy rolls.Comment: 8 pages and 3 figures, late
Asymmetric Squares as Standing Waves in Rayleigh-Benard Convection
Possibility of asymmetric square convection is investigated numerically using
a few mode Lorenz-like model for thermal convection in Boussinesq fluids
confined between two stress free and conducting flat boundaries. For relatively
large value of Rayleigh number, the stationary rolls become unstable and
asymmetric squares appear as standing waves at the onset of secondary
instability. Asymmetric squares, two dimensional rolls and again asymmetric
squares with their corners shifted by half a wavelength form a stable limit
cycle.Comment: 8 pages, 7 figure
Transition from the Couette-Taylor system to the plane Couette system
We discuss the flow between concentric rotating cylinders in the limit of
large radii where the system approaches plane Couette flow. We discuss how in
this limit the linear instability that leads to the formation of Taylor
vortices is lost and how the character of the transition approaches that of
planar shear flows. In particular, a parameter regime is identified where
fractal distributions of life times and spatiotemporal intermittency occur.
Experiments in this regime should allow to study the characteristics of shear
flow turbulence in a closed flow geometry.Comment: 5 pages, 5 figure
Resonant enhanced diffusion in time dependent flow
Explicit examples of scalar enhanced diffusion due to resonances between
different transport mechanisms are presented. Their signature is provided by
the sharp and narrow peaks observed in the effective diffusivity coefficients
and, in the absence of molecular diffusion, by anomalous transport. For the
time-dependent flow considered here, resonances arise between their
oscillations in time and either molecular diffusion or a mean flow. The
effective diffusivities are calculated using multiscale techniques.Comment: 18 latex pages, 11 figure
Treatment of cystoid macular edema with the new-generation NSAID nepafenac 0.1%
Seenu M Hariprasad1, Levent Akduman2, Joseph A Clever2, Michael Ober3,4, Franco M Recchia5, William F Mieler1,61Department of Ophthalmology and Visual Sciences, Vitreoretinal Service; 6Department of Ophthalmology and Visual Sciences, University of Chicago, Chicago, IL, USA; 2Vitreoretinal Service, Saint Louis University Eye Institute, Saint Louis, MO, USA; 3Vitreoretinal Service, Henry Ford Health Systems, West Bloomfield, MI, USA; 4Retinal Consultants of Michigan, Southfield, MI, USA; 5Vitreoretinal Service, Vanderbilt Eye Institute, Nashville, TN, USAPurpose: To describe the use of nepafenac 0.1% for cystoid macular edema (CME).Methods: This was a multicenter retrospective review of 22 CME cases (20 patients) treated with nepafenac 0.1% (six with concomitant prednisolone acetate 1%) from December 2005 to April 2008: three acute pseudophakic CME cases, 13 chronic/recalcitrant pseudophakic CME cases, and six cases of uveitic CME. Pre- and post-treatment retinal thickness and visual acuity were reported.Results: Following treatment for six weeks to six months, six eyes with uveitic CME showed a mean retinal thickness improvement of 227 ± 168.1 μm; mean best-corrected visual acuity (BCVA) improvement was 0.36 ± 0.20 logMAR. All three cases of acute pseudophakic CME improved after four to 10 weeks of nepafenac, with a mean improvement in retinal thickness of 134 ± 111.0 μm. BCVA improved in two patients (0.16 and 0.22 logMAR) but not in the third due to underlying retinal pigment epithelium changes. Thirteen eyes with chronic/recalcitrant pseudophakic CME demonstrated a mean improvement in retinal thickness of 178 ± 128.7 μm after nepafenac and mean BCVA improvement of 0.33 ± 0.19 logMAR.Conclusion: The positive outcomes of these 22 eyes strongly suggest that nepafenac 0.1% is a promising drug for the treatment of CME. Additional study under randomized controlled conditions is warranted.Keywords: macular edema, NSAID, nepafenac, cataract surgery, uveiti
- …