4,197 research outputs found
Computer program simplifies design of rotating components of turbomachinery
Digital computer program performs stress analysis and burst speed calculations on rotating axisymmetric turbomachinery components. The computer printout contains the displacement of each nodal point, the stress at the center of each element, the average tangential stress within the component, and the burst speed
Analysis of longitudinal bunching inan FEL driven two-beam accelerator
Recent experiments [1] have explored the use of a free-electron laser (FEL)
as a buncher for a microwave two-beam accelerator, and the subsequent driving
of a standing-wave rf output cavity. Here we present a deeper analysis of the
longitudinal dynamics of the electron bunches as they are transported from the
end of the FEL and through the output cavity. In particular, we examine the
effect of the transport region and cavity aperture to filter the bunched
portion of the beam.
[1] T. Lefevre, et. al., Phys. Rev. Lett. 84 (2000), 1188.Comment: 3 pages, 8 figures. Submitted to XX Int'l LINAC Conferenc
2-Dust : a Dust Radiative Transfer Code for an Axisymmetric System
We have developed a general purpose dust radiative transfer code for an
axisymmetric system, 2-Dust, motivated by the recent increasing availability of
high-resolution images of circumstellar dust shells at various wavelengths.
This code solves the equation of radiative transfer following the principle of
long characteristic in a 2-D polar grid while considering a 3-D radiation field
at each grid point. A solution is sought through an iterative scheme in which
self-consistency of the solution is achieved by requiring a global luminosity
constancy throughout the shell. The dust opacities are calculated through Mie
theory from the given size distribution and optical properties of the dust
grains. The main focus of the code is to obtain insights on (1) the global
energetics of dust grains in the shell (2) the 2-D projected morphologies that
are strongly dependent on the mixed effects of the axisymmetric dust
distribution and inclination angle of the shell. Here, test models are
presented with discussion of the results. The code can be supplied with a
user-defined density distribution function, and thus, is applicable to a
variety of dusty astronomical objects possessing the axisymmetric geometry.Comment: To be published in ApJ, April 2003 issue; 13 pages, 4 tables, 17
figures, 5-page appendix (no figures for the main text included in this
preprint). For the complete preprint and code distribution, contact the
author
Scanning Transmission Ion Microscopy as it Complements Particle Induced X-Ray Emission Microanalysis
The early uses of Scanning Transmission Ion Microscopy (STIM) with MeV ions are reviewed. The transformation of STIM energy-loss images into maps of areal density is discussed, and is illustrated with images of a fruit fly head (Drosophila melanogaster). Freeze-dried male heads are transparent to 4-MeV protons in the dorsal and frontal directions, but in the sagittal direction the brain is opaque. STIM with molecular ions is shown to be useful for increasing contrast in low density areas. For recording registered STIM and PIXE images without changing accelerator parameters, apertures are used to accomplish the required change in beam intensity (a factor of 105). Molecular ions are used to assess contamination of the microbeam by scattered ions. Pixel by pixel ratios of x-ray intensity to areal density are taken to obtain maps of element concentrations. Calcium and iron maps are shown. Inner parts of the fly head are clearly seen in the concentration maps. The PIXE exposure caused differential displacements of inner parts of the head by 15 μm or less. Weight loss during the PIXE exposure was measured to be 3%
Developing a Relationship Between LIBS Spectra and Pit Volume for in Situ Dating of Geologic Samples
No abstract availabl
Relationship Between LIBS Ablation and Pit Volume for Geologic Samples: Applications for the In Situ Absolute Geochronology
These first results demonstrate that LIBS spectra can be an interesting tool to estimate the ablated volume. When the ablated volume is bigger than 9.10(exp 6) cubic micrometers, this method has less than 10% of uncertainties. Far enough to be directly implemented in the KArLE experiment protocol. Nevertheless, depending on the samples and their mean grain size, the difficulty to have homogeneous spectra will increase with the ablated volume. Several K-Ar dating studies based on this approach will be implemented. After that, the results will be shown and discussed
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