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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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Journal ArticleDOI
TL;DR: It is demonstrated that the dosimetric properties of high-energy photon emitters are largely dependent on radionuclide source distribution.
Abstract: Monte Carlo based dosimetry is presented for three 60 Co HDR sources with a unique configuration of two active pellets in contact or spaced 9 and 11 mm apart. Results are presented in Cartesian “away and along” as well as polar coordinates following the AAPM TG-43 dosimetric formalism. Iso-dose rate contours around the sources in Cartesian coordinates reveal that significant differences between the three source designs exist only close to the source centers where dose rate distributions bear the effect of the unique source configurations. Dose rate constants of all three sources are accurately described by an equation of the form: Λ( cGy h −1 U −1 )=Λ point * G(1 cm ,90°)=1.094 * G(1 cm,90°) where Λ point is the dose rate constant of a bare 60 Co point source and G(1 cm,90°) is the “exact” source geometry factor as defined by the TG-43. Radial dose and anisotropy function data extracted using the point source approximated geometry factors are tabulated for all three source designs. Finally, the dependence and variation of the above TG-43 parameters are discussed and it is demonstrated that the dosimetricproperties of high-energy photon emitters are largely dependent on radionuclide source distribution.

44 citations

Journal ArticleDOI
TL;DR: In this article, the stiffness tensor coefficients of anisotropic materials are recovered by scanning a symmetry plane, and four coefficients of the tensor are then recovered with good reliability.
Abstract: A scanned point source‐point receiver technique, based on laser generation and detection of acoustic waves, is used to measure the stiffness coefficients of anisotropic materials. The striking effects that anisotropy gives rise to are analyzed and, when possible, advantage is taken of them. The processing developed for recovering the coefficients is presented and applied starting with simulated or experimental signals. A silicon crystal, for which acoustic wave focusing induced by anisotropy is critically sensitive, is first studied. To provide an accurate interpretation of these waves, the two‐dimensional problem considering a line source is discussed, before analyzing the point source generation. Secondly, a manufactured composite material is characterized by means of this noncontact technique. By scanning a symmetry plane, four coefficients of the stiffness tensor are then recovered with good reliability.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a harmonic point source of sound was placed within the potential core of an air jet and the distortion of its sound field by the jet flow was measured, and it was shown that the cleft in the heart-shaded directivity pattern of subsonic jet noise can be attributed mainly to refraction.
Abstract: A harmonic point source of sound was placed within the potential core of an air jet and the distortion of its sound field by the jet flow was measured. An axial intensity minimum was observed that increases with increasing velocity, frequency, or temperature. The investigation indicates that the cleft in the heart‐shaded directivity pattern of subsonic jet noise can be attributed mainly to refraction.

44 citations

Journal ArticleDOI
TL;DR: In this article, a simple flow model and solution to describe "horizontal convection" driven by a gradient of temperature or heat flux along one horizontal boundary of a rectangular box is presented.
Abstract: We present a simple flow model and solution to describe ‘horizontal convection’ driven by a gradient of temperature or heat flux along one horizontal boundary of a rectangular box. Following laboratory observations of the steady-state convection, the model is based on a localized vertical turbulent plume from a line or point source that is located anywhere within the area of the box and that maintains a stably stratified interior. In contrast to the ‘filling box’ process, the convective circulation involves vertical diffusion in the interior and a stabilizing buoyancy flux distributed over the horizontal boundary. The stabilizing flux forces the density distribution to reach a steady state. The model predictions compare well with previous laboratory data and numerical solutions. In the case of a point source for the plume (the case which best mimics the localized sinking in the large-scale ocean overturning) the thermal boundary layer is much thicker than that given by the two-dimensional boundary layer scaling of H. T. Rossby (Tellus, vol. 50, 1965, p. 242).

44 citations

01 Jan 1979
TL;DR: In this paper, the axisymmetric velocity and temperature fields associated with a point source of thermal energy in a fluid-saturated porous medium are obtained numerically through use of similarity transformations.
Abstract: Solutions for the axisymmetric velocity and temperature fields associated with a point source of thermal energy in a fluid-saturated porous medium are obtained numerically through use of similarity transformations. The two cases considered are those of a point source located on the lower boundary of a semi-infinite region and a point source embedded in an infinite region. Tabulated results are presented from which complete descriptions of the velocity and temperature fields can be constructed for Rayleigh numbers of 0.1, 1, 10, and 100.

43 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202350
2022133
2021103
2020135
2019123
2018133