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Point source
About: Point source is a research topic. Over the lifetime, 5077 publications have been published within this topic receiving 94091 citations.
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TL;DR: In this article, the advective diffusive equation around a three dimensional hill which is axisymmetric about a vertical axis is solved to show how source positions on and off the center line affect the trajectories and splitting of impinging plumes and the value and position of the maximum surface concentration on the hill.
49 citations
TL;DR: In this article, a general theory of radio propagation by wave-guide modes is given, which simultaneously makes allowance for the gradualness of the lowest part of the ionosphere, the earth's curvature and the earth magnetic field.
Abstract: A general theory of radio propagation by wave-guide modes is given, which simultaneously makes allowance for the gradualness of the lowest part of the ionosphere, the earth’s curvature and the earth’s magnetic field. The method involves solving differential equations satisfied by the matrix admittance or matrix reflexion coefficient variables. The mode condition, excitation factor, and polarization of the waves in a mode are derived by evaluating the residues of a series of poles of a contour integral. The earth’s curvature is allowed for by the method of the ‘modified refractive index’, thus avoiding the use of cumbersome spherical wave functions. This also permits the replacement of a point source by a line source with consequent further simplification of the mathematics. Formulae are given which have been used for computations described elsewhere (Budden & Martin 1962; Martin 1961).
49 citations
TL;DR: In this article, an evaluation of the optical transition radiation (OTR) single particle image dimension is obtained using diffraction theory based on a realistic description of the radiation source, which allows the analysis of the effect of the finite size of the emitting screen and of the imaging system.
Abstract: An evaluation of the optical transition radiation (OTR) single particle image dimension is obtained using diffraction theory based on a realistic description of the radiation source. This approach allows the analysis of the effect of the finite size of the emitting screen and of the imaging system. The role of practical experimental conditions in treating the intensity tail problem is estimated. It is shown that, by exploiting the polarization properties of OTR, a considerable enhancement in the spatial resolution can be achieved, which becomes very similar to that of a standard point source.
49 citations
TL;DR: In this paper, an experimental investigation of turbulent dispersion of a saline plume of large Schmidt number (Sc=830) in a turbulent boundary-layer shear flow simulated in a laboratory water channel is presented.
Abstract: Results are presented from an experimental investigation of turbulent dispersion of a saline plume of large Schmidt number (Sc=830) in a turbulent boundary-layer shear flow simulated in a laboratory water channel The dispersion measurements are obtained in a neutrally buoyant plume from an elevated point source over a range of downstream distances, where both plume meandering and fine-structure variations in the instantaneous plume are important High-resolution measurements of the scalar fluctuations in the plume are made with a rake of conductivity probes from which probability distributions of concentration at various points throught the plume are extracted from the time series
49 citations
TL;DR: In this article, the average upper limit over the northern sky for point sources of muon-neutrinos with E-2 spectrum is E^2 Phi_nu_mu < 1.4x10^-11 TeV cm^-2 s^-1, in the energy range from 3 TeV to 3 PeV.
Abstract: We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-08 with 22 strings of the IceCube detector (approximately one-fourth of the planned total) and 275.7 days of livetime. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2 sigma after accounting for all trials. The average upper limit over the northern sky for point sources of muon-neutrinos with E^-2 spectrum is E^2 Phi_nu_mu < 1.4x10^-11 TeV cm^-2 s^-1, in the energy range from 3 TeV to 3 PeV, improving the previous best average upper limit by the AMANDA-II detector by a factor of two.
49 citations