34,450 research outputs found
General aviation crash safety program at Langley Research Center
The purpose of the crash safety program is to support development of the technology to define and demonstrate new structural concepts for improved crash safety and occupant survivability in general aviation aircraft. The program involves three basic areas of research: full-scale crash simulation testing, nonlinear structural analyses necessary to predict failure modes and collapse mechanisms of the vehicle, and evaluation of energy absorption concepts for specific component design. Both analytical and experimental methods are being used to develop expertise in these areas. Analyses include both simplified procedures for estimating energy absorption capabilities and more complex computer programs for analysis of general airframe response. Full-scale tests of typical structures as well as tests on structural components are being used to verify the analyses and to demonstrate improved design concepts
Pulsed energy power system Patent
Pulsed energy power system for application of combustible gases to turbine controlling ac voltage generato
Observation of robust flat-band localization in driven photonic rhombic lattices
We demonstrate that a flat-band state in a quasi-one-dimensional rhombic
lattice is robust in the presence of external drivings along the lattice axis.
The lattice was formed by periodic arrays of evanescently coupled optical
waveguides, and the external drivings were realized by modulating the paths of
the waveguides. We excited a superposition of flat-band eigenmodes at the input
and observed that this state does not diffract in the presence of static as
well as high-frequency sinusoidal drivings. This robust localization is due to
destructive interference of the analogous wavefunction and is associated with
the symmetry in the lattice geometry. We then excited the dispersive bands and
observed Bloch oscillations and coherent destruction of tunneling.
{\textcopyright} 2017 Optical Society of America.Comment: 5 pages, 7 figure
NASA/FAA general aviation crash dynamics program
The program involves controlled full scale crash testing, nonlinear structural analyses to predict large deflection elastoplastic response, and load attenuating concepts for use in improved seat and subfloor structure. Both analytical and experimental methods are used to develop expertise in these areas. Analyses include simplified procedures for estimating energy dissipating capabilities and comprehensive computerized procedures for predicting airframe response. These analyses are developed to provide designers with methods for predicting accelerations, loads, and displacements on collapsing structure. Tests on typical full scale aircraft and on full and subscale structural components are performed to verify the analyses and to demonstrate load attenuating concepts. A special apparatus was built to test emergency locator transmitters when attached to representative aircraft structure. The apparatus is shown to provide a good simulation of the longitudinal crash pulse observed in full scale aircraft crash tests
Okun's Law and Movements over Time in the Unemployment Rate in Australia.
This article explains how movements in the unemployment rate reflect the relative rates of growth of employment and the labour force and are related to the participation rate, labour productivity growth and output growth. A framework is provided in which to analyse the determinants of movements in the unemployment rate. We look at the unemployment rate and its relationship to labour force and employment growth in the next section. In section 3 we define the participation rate and discuss how it relates to labour force growth. Then in Section 4, we consider Verdoon's Law and the relationship between output growth and employment growth. In Section 5 we combine the results in the previous section to determine the relationship between the unemployment rate and output growth. Finally, in Section 6, we summarise the findings. We begin looking at these questions by considering the way in which we measure the unemployment rate.UNEMPLOYMENT ; ECONOMIC THEORY ; MACROECONOMICS
An evaluation of errors observed in the measurement of low wind velocities
Measurements of low wind velocities (the absolute value of V sub H is approx. equal to 6 m/s) with a VHF wind profiler can be difficult if ground clutter or other biases in the system dominate in altering the position of the perceived peak in the calculated power spectrum. A variety of methods for ground clutter suppression are used in profiler systems today (Cornish, 1983). An editing method called zero suppression takes the spectral value of selectable number of points (N) on each side of 0 velocity (one point on either side, in this study) and sets them equal to the mean value of the points exterior to the specified N points on either side of 0. Analysis done with the PSU VHF(1) radar, shows that this zero-suppression method can systematically bias horizontal wings V sub H below 6 m/s. With the zero suppression, an artificial increase in absolute wind velocities occurs when the spectral peaks fall within the plus or minus N points of the FFT (personal communication, Strauch, 1985). It was also established that the method artificially decreases the absolute wind velocities inferred from spectral peaks that are outside but near the suppressed region. Comparisons of wind profiles observed with and without zero suppression are given. The range of the biased velocities extends to about plus or minus 6 m/s. Biases have been deduced to be as much as 2 m/s, but more commonly they are on the order of 1.0 m/s
Structural response of transport airplanes in crash situations
This report highlights the results of contractural studies of transport accident data undertaken in a joint research program sponsored by the FAA and NASA. From these accident data studies it was concluded that the greatest potential for improved transport crashworthiness is in the reduction of fire related fatalities. Accident data pertaining to fuselage integrity, main landing gear collapse, fuel tank rupture, wing breaks, tearing of tank lower surfaces, and engine pod scrubbing are discussed. In those accidents where the energy absorbing protective capability of the fuselage structure is expended and the airplane experiences major structural damage, trauma caused fatalities are also discussed. The dynamic performance of current seat/restraint systems are examined but it is concluded that the accident data does not adequately define the relationship between occupant response and the dynamic interaction with the seat, floor and fuselage structure
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