14,477 research outputs found
An Optical Altitude Indicator for Night Landing
One of the most ingenious of the devices intended for use in night landing, especially emergency landing, is a very simple optical instrument known as the Jenkins night altitude indicator. The design and operation of this instrument, which allows a pilot to determine the altitude of the aircraft, is discussed. The author discusses various modifications and improvements that might be made to the instrument
Finite element solution of low bond number sloshing
The dynamics of liquid propellant in a low Bond number environment which are critical to the design of spacecraft systems with respect to orbital propellant transfer and attitude control system were investigated. Digital computer programs were developed for the determination of liquid free surface equilibrium shape, lateral slosh natural vibration mode shapes, and frequencies for a liquid in a container of arbitrary axisymmetric shape with surface tension forces the same order of magnitude as acceleration forces. A finite volume element representation of the liquid was used for the vibration analysis. The liquid free surface equilibrium shapes were computed for several tanks at various contact angles and ullage volumes. A configuration was selected for vibration analysis and lateral slosh mode shapes and natural frequencies were obtained. Results are documented
The Hilbert Action in Regge Calculus
The Hilbert action is derived for a simplicial geometry. I recover the usual
Regge calculus action by way of a decomposition of the simplicial geometry into
4-dimensional cells defined by the simplicial (Delaunay) lattice as well as its
dual (Voronoi) lattice. Within the simplicial geometry, the Riemann scalar
curvature, the proper 4-volume, and hence, the Regge action is shown to be
exact, in the sense that the definition of the action does not require one to
introduce an averaging procedure, or a sequence of continuum metrics which were
common in all previous derivations. It appears that the unity of these two dual
lattice geometries is a salient feature of Regge calculus.Comment: 6 pages, Plain TeX, no figure
Partial Dynamical SU(3) Symmetry and the Nature of the Lowest K=0 Collective Excitation in Deformed Nuclei
We discuss the implications of partial dynamical SU(3) symmetry (PDS) for the
structure of the lowest K=0^{+} (K=0_2) collective excitation in deformed
nuclei. We consider an interacting boson model Hamiltonian whose ground and
gamma bands have good SU(3) symmetry while the K=0_2 band is mixed. It is shown
that the double-phonon components in the K=0_2 wave function arise from SU(3)
admixtures which, in turn, can be determined from absolute E2 rates connecting
the K=0_2 and ground bands. An explicit expression is derived for these
admixtures in terms of the ratio of K=0_2 and gamma bandhead energies. The
SU(3) PDS predictions are compared with existing data and with broken-SU(3)
calculations for ^{168}Er.Comment: 12 pages, 2 figure
Absolute Calibration of the Auger Fluorescence Detectors
Absolute calibration of the Pierre Auger Observatory fluorescence detectors
uses a light source at the telescope aperture. The technique accounts for the
ombined effects of all detector components in a single measurement. The
calibrated 2.5 m diameter light source fills the aperture, providing uniform
illumination to each pixel. The known flux from the light source and the
response of the acquisition system give the required calibration for each
pixel. In the lab, light source uniformity is studied using CCD images and the
intensity is measured relative to NIST-calibrated photodiodes. Overall
uncertainties are presently 12%, and are dominated by systematics.Comment: 4 pages, 3 figure. Submitted to the 29th ICRC, Pune, Indi
Ellipsometric and optical study of some uncommon insulator films on 3-5 semiconductors
Optical properties of three types of insulating films that show promise in potential applications in the 3-4 semiconductor technology were evaluated, namely a-C:H, BN and CaF2. The plasma deposited a-C:H shows an amorphous behavior with optical energy gaps of approximately 2 to 2.4 eV. These a-C:H films have higher density and/or hardness, higher refractive index and lower optical energy gaps with increasing energy of the particles in the plasma, while the density of states remains unchanged. These results are in agreement, and give a fine-tuned positive confirmation to an existing conjecture on the nature of a-C:H films (1). Ion beam deposited BN films show amorphous behavior with energy gap of 5 eV. These films are nonstoichiometric (B/N approximately 2) and have refractive index, density and/or hardness which are dependent on the deposition conditions. The epitaxially grown CaF2 on GaAs films have optical parameters equal to bulk, but evidence of damage was found in the GaAs at the interface
The super algebra and its associated generalized KdV hierarchies
We construct the super algebra as a certain reduction of the
second Gel'fand-Dikii bracket on the dual of the Lie superalgebra of
super pseudo-differential operators. The algebra is put in manifestly
supersymmetric form in terms of three superfields , with
being the energy momentum tensor and and being
conformal spin and superfields respectively. A search for integrable
hierarchies of the generalized KdV variety with this algebra as Hamiltonian
structure gives three solutions, exactly the same number as for the
(super KdV) and (super Boussinesq) cases.Comment: 16 pages, LaTeX, UTAS-PHYS-92-3
Microgeographic Variation in Response of Red-Eared Slider (Trachemys scripta elegans) Embryos to Similar Incubation Environments
We examined site-specific variation in the response of red-eared slider (Trachemys elegans) embryos exposed to similar incubation environments, and collected at five nearby sites central Illinois. Overall, site was not a significant source of variance in change in egg mass during bation, in hatchling wet mass, and in hatchling carapace length. However, site was a significant source variance in incubation period. Nonetheless, significant site-specific differences in each trait were in pairwise comparisons. The actual difference between extremes was small. Eggs from the site longest incubation period also gained the most water during incubation. Our study has important cations for future studies of geographic variation in the physiological response of embryos to incubation environments. Comparisons between eggs and embryos from geographically distant sites would benefit inclusion of as many clutches as possible. Larger numbers of clutches reduce the possibility that ferences between geographically distant regions are due to maternal differences rather than region-differences. Studies comparing embryonic responses from geographically distant regions would be strengthened by including turtles from as many local collecting sites for each region as possible. Sampling site per region may be inadequate because any geographic variation in embryonic response could well be due to undetected local site-specific differences
Cryptographic Randomized Response Techniques
We develop cryptographically secure techniques to guarantee unconditional
privacy for respondents to polls. Our constructions are efficient and
practical, and are shown not to allow cheating respondents to affect the
``tally'' by more than their own vote -- which will be given the exact same
weight as that of other respondents. We demonstrate solutions to this problem
based on both traditional cryptographic techniques and quantum cryptography.Comment: 21 page
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