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Summary Time-dependent waveforms are commonly extrapolated in space by means of rays and occasionally by means of diffraction integrals. It is possible to extrapolate time-dependent waves in space with a partial differential equation derived from the wave equation. There are stable numerical approximations. An example illustrates a mechanism for 'signal-generated noise' which is consistent with observations. 相似文献
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Jon Darius 《Astrophysics and Space Science》1984,99(1-2):273-279
Binary systems displaying spectroscopic segregation, whereby line spectra of the two components overlap little or not at all in wavelength, account for a small subset of LUV objects (late-type ultraviolet). Optical and ultraviolet (IUE) spectra for one such system, HD 15351+UV0225+13 (F4-5 V+sdO), are presented and a few related systems described. The role of LUV objects in establishing an absolute luminosity calibration for hot subdwarfs is emphasized, along with their significance for stellar evolution. A search strategy for additional spectroscopically segregated LUV objects is outlined.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983. 相似文献
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We propose a two-dimensional Lagrangian analytical solution for relating source strength and concentration profiles within
and above a plant canopy. The new solution describes passive scalar dispersion under conditions of local advection through
a fetch correction function in a one-dimensional Lagrangian analytical dispersion model. The model is capable of predicting
absolute concentration profiles of passive scalars for different fetches for situations in which the reference concentration
is known or the background concentration is available. Tests of the model showed good agreement with measurements from field
and wind-tunnel experiments. 相似文献
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A method to identify special and/or unique sites was developed when reviewing the zoning of the Great Barrier Reef Marine Park. Fifty-three (totalling approximately 10,445 km2) of 408 sites were identified as special or unique based on the amount, detail and nature of justification; geographic explicitness; type of information sources; number of independent sources; and national or international obligations. All but four special or unique sites increased in protection after the Zoning Plan was revised, increasing the area of no-take protection for all special or unique sites from 1614 km2 (15.4%) to 4013 km2 (38.4%). 相似文献