2,248 research outputs found
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Performance of a self-lifting linear air contact
An investigation into the performance of a self-levitating linear air bearing that functions on the squeeze film principle was conducted and a detailed set of results describing its floating characteristics at various operating parameters is presented. Experimentally assessed performance of the bearing was compared with performance predicted by a computer model of the bearing
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Surface damage resulting from rolling contact operating in magnetic field
This paper describes the effects of magnetic field in rolling contact tests of steel by using a two-disc configuration and the investigation of mechanisms involved.
Two contact conditions, namely pure rolling and rolling with 10% sliding were used together with 0.4 and 1.1 Tesla horizontal static magnetic fields created by permanent magnets. Results of optical and scanning electron microscope observations point out that finer wear particles and smoother worn surfaces are produced in the presence of a magnetic field. It is proposed that finer wear particles result from the movement of subsurface crack initiation towards the surface due to the action of magnetic field
Uncertainty calculations and their relationship to the problem of early detection of ozone change
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Squeeze-film levitation characteristics of plates excited by piezoelectric actuators
A small mass is levitated by a vibrating plate with an arrangement of four piezoelectric actuators that generate a squeeze-film in the gap between the plate and the mass. Different arrangements of actuators and plate design are explored using simulation in order to produce better performance
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Plate actuator vibration modes for levitation
The design of an aluminium or steel plate of various thicknesses for achieving levitation of a small aluminum disk is investigated by simulation using ANSYS. Each plate design is excited by an arrangement of four hard piezoelectric actuators driven with an AC voltage, which produces a centre displacement for generating a squeeze-film in the gap between the vibrating plate and the disk. Physical experiments show levitation conditions for one of the designs
New Measurements with Stopped Particles at the LHC
Metastable particles are common in many models of new physics at the TeV
scale. If charged or colored, a reasonable fraction of all such particles
produced at the LHC will stop in the detectors and give observable out of time
decays. We demonstrate that significant information may be learned from such
decays about the properties (e.g. charge or spin) of this particle and of any
other particles to which it decays, for example a dark matter candidate. We
discuss strategies for measuring the type of decay (two- vs three-body), the
types of particles produced, and the angular distribution of the produced
particles using the LHC detectors. We demonstrate that with O(10-100) observed
decay events, not only can the properties of the new particles be measured but
indeed even the Lorentz structure of the decay operator can be distinguished in
the case of three-body decays. These measurements can not only reveal the
correct model of new physics at the TeV scale, but also give information on
physics giving rise to the decay at energy scales far above those the LHC can
probe directly.Comment: 31 pages, 6 figures. References added, updated to reflect recent
experimental results, version accepted for publication in Physical Review
Present state of knowledge of the upper atmosphere: An assessment report; processes that control ozone and other climatically important trace gases
The state of knowledge of the upper atmosphere was assessed as of January 1986. The physical, chemical, and radiative processes which control the spatial and temporal distribution of ozone in the atmosphere; the predicted magnitude of ozone perturbations and climate changes for a variety of trace gas scenarios; and the ozone and temperature data used to detect the presence or absence of a long term trend were discussed. This assessment report was written by a small group of NASA scientists, was peer reviewed, and is based primarily on the comprehensive international assessment document entitled Atmospheric Ozone 1985: Assessment of Our Understanding of the Processes Controlling Its Present Distribution and Change, to be published as the World Meteorological Organization Global Ozone Research and Monitoring Project Report No. 16
Theoretical modelling and meteorological analysis for the AASE mission
Providing real time constituent data analysis and potential vorticity computations in support of the Airborne Arctic Stratospheric Experiment (AASE) is discussed. National Meteorological Center (NMC) meteorological data and potential vorticity computations derived from NMC data are projected onto aircraft coordinates and provided to the investigators in real time. Balloon and satellite constituent data are composited into modified Lagrangian mean coordinates. Various measurements are intercompared, trends deduced and reconstructions of constituent fields performed
Assessment of possible environmental effects of space shuttle operations
The potential of shuttle operations to contribute to atmospheric pollution is investigated. Presented in this interim report are results of the study to date on rocket exhaust inventory, exhaust interactions, dispersion of the ground cloud, detection and measurement of hydrochloric acid and aluminum oxide, environmental effects of hydrochloric acid and aluminum oxide, stratospheric effects of shuttle effluents, and mesospheric and ionospheric effects of orbiter reentry. The results indicate space shuttle operation will not result in adverse environmental effects if appropriate launch constraints are met
The QBO and interannual variation in total ozone
Garcia and Soloman (1987) have noted that the October monthly mean minimum total ozone amounts south of 30 S were modulated by a quasibiennial oscillation (QBO) signal. The precise mechanism behind this effect, however, is unclear. Is the modulation brought about by the circulation-produced QBO signal in the ozone concentration itself, or does the temperature QBO modulate the formation of polar stratospheric clouds (PSCs), leading to changes in the chemically induced Antarctic spring ozone decline rate. Or is some other phenomenon involved. To investigate the means through which the QBO effect occurs, a series of correlation studies has been made between polar ozone and QBO signal in ozone and temperature
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