Determination of point source mechanisms

This paper shows t h a t given certain conditions it is perfectly feasible to study an earthquake that occurred three-quarters of a century ago in a remote part of the world. Also, it shows that there are many large earthquakes which, because of lack of interdisciplinary efforts to study such events, have remained hitherto little known or totally unknown. The case of the Silakhor earthquake revealed deficiencies in the determination of epicentres by ISS and Gutenberg; the difference between macroseismic and instrumental position for the Silakhor earthquake is 380 kilometres, a difference which lias caused a serious problem in the assessment of seisniicity of Iran. Accurate macroseismic d a t a may be used to minimize bias in t h e instrumental relocation of the larger events and to study source mechanisms. Untili this study was undertaken, the faulting associated with the Silakhor earthquake was totally unknown. Even more important t h a n the value of recent faulting for its significance in resolving ambiguities in t h e choice of the t r u e source parametres, is the information that can be gleaned from evidence for the mechanism of earthquakes that occurred long before t h e advent of modern seismology and in particular, for the pattern of recent tectonic activity.

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Simultaneous, maximum-likelihood determination of focal length and source position for point-source experiments with pinhole collimation

IEEE Symposium Conference Record Nuclear Science 2004. ◽

10.1109/nssmic.2004.1466656 ◽

2005 ◽

Author(s):

S.D. Metzler ◽

N.H. Patil ◽

R. Accorsi

Keyword(s):

Maximum Likelihood ◽

Point Source ◽

Focal Length ◽

Source Position

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Image Reconstruction from VLBI Amplitude and Phase Closure Data

International Astronomical Union Colloquium ◽

10.1017/s0252921100074777 ◽

1979 ◽

Vol 49 ◽

pp. 93-93

Author(s):

William D. Cotton ◽

Jill J. Wittels

Keyword(s):

Point Source ◽

Direct Synthesis ◽

Angular Structure ◽

Long Baseline ◽

Test Models ◽

Step Procedure ◽

Source Convergence ◽

Using Data ◽

Starting Model

AbstractA two step procedure is developed for the determination of the angular structure of the compact components of radio sources from observations made with very long baseline interferometry (VLBI). The first step is to fit a model composed of circularly symmetric Gaussian components to the observations. Then this, or any other, model and closure phase information is used to predict visibility phases which, when paired with the corresponding visibility amplitude observation, are combined in a direct synthesis; the resulting map is deconvolved from the point source response by means of the “CLEAN” procedure. If necessary, the “cleaned” components can be used as a starting model to predict visibility phases and the process iterated. The initial model in many cases may be as simple as a point source. Convergence of this process appears to be quite rapid, requiring only a few iterations when the source is simple or the starting model is good. These two steps for source mapping can be used either together or separately. Examples are given using data generated from test models.

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Modelling the thermal radiation from kitchen hob fires

Journal of Fire Sciences ◽

10.1177/0734904120923566 ◽

2020 ◽

Vol 38 (4) ◽

pp. 377-394

Author(s):

Michael Spearpoint ◽

Charlie Hopkin ◽

Danny Hopkin

Keyword(s):

Heat Flux ◽

Point Source ◽

Radial Distance ◽

Source Model ◽

View Factor ◽

Calculation Methods ◽

Fire Dynamics ◽

Potential Threat ◽

Computational Tools

Kitchen hob fires present a potential threat to occupants escaping from dwellings and calculations may be needed to assess the hazard. Determination of the thermal heat flux from flames to a target can be achieved through the use of hand calculation methods or computational tools. This article compares point source, parallel plane and cylindrical view factor hand calculations and computational simulations using B-RISK and Fire Dynamics Simulator of thermal heat flux with kitchen hob fire experiments presented in the literature. Knowing the level of accuracy of each method provides useful information to designers. Although the point source model is influenced by whether the radial distance is measured perpendicular to the heat flux target or is offset relative to the centre of the flame, the article concludes that it provides an adequate approach for the calculation of thermal heat flux in the case of kitchen hob fires.

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