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212 results on '"Hanson, Kenneth M."'

2. Lessons about likelihood functions from nuclear physics

Author

Hanson, Kenneth M.

Subjects
Nuclear Experiment
Abstract

Least-squares data analysis is based on the assumption that the normal (Gaussian) distribution appropriately characterizes the likelihood, that is, the conditional probability of each measurement d, given a measured quantity y, p(d | y). On the other hand, there is ample evidence in nuclear physics of significant disagreements among measurements, which are inconsistent with the normal distribution, given their stated uncertainties. In this study the histories of 99 measurements of the lifetimes of five elementary particles are examined to determine what can be inferred about the distribution of their values relative to their stated uncertainties. Taken as a whole, the variations in the data are somewhat larger than their quoted uncertainties would indicate. These data strongly support using a Student t distribution for the likelihood function instead of a normal. The most probable value for the order of the t distribution is 2.6 +/- 0.9. It is shown that analyses based on long-tailed t-distribution likelihoods gracefully cope with outlying data., Comment: presented at 27th International Workshop on Bayesian Inference and Maximum Entropy Methods in Science and Engineering (Maxent 2007), 10 pages, 12 figures

Published
2007
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5. The Hard Truth

Author

Hanson, Kenneth M., Cunningham, Gregory S., Van der Merwe, Alwyn, editor, Skilling, John, editor, and Sibisi, Sibusiso, editor

Published
1996
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11. Improving display quality by a digital convergence correction system for multibeam CRTs

Author

Barels, J.K. Patrick, Lubbers, Lex, Slump, Cornelis, Kemner, Rudolf, Hoeven, Aartjan, Loew, Murray H., and Hanson, Kenneth M.

Subjects
Luminance, Brightness, Resolution, Convergence, Multiple beam, Cathode ray tube, Interpolation
Abstract

In the field of medical imaging there is a need for high-resolution high-brilliance monochromatic CRT displays. However, at higher brightness levels the resolution of these displays decreases, due to the increasing spot size. In order to improve the performance of the CRT display a relatively simple method, called the multi-beam concept, is introduced. Using this technique a higher brightness can be realized without an increase of the spot size and therefore a better display quality can be achieved. However, for successful exploitation of the multi-beam concept it is necessary to minimize the convergence error of the CRT display. For this purpose two circuits have been realized, where the convergence error is reduced by an analogue and a digital method respectively. The analogue implementation means an improvement for the applicability of the multi-beam concept, however, in order to achieve major image quality improvement the use of the digital system is necessary.

Published
1996

22. Inference from Rossi traces.

Author

Hanson, Kenneth M. and Booker, Jane M.

Subjects
*OSCILLOSCOPES, *PHYSICS
Abstract

We present an uncertainty analysis of data taken using the Rossi technique in which the horizontal oscilloscope sweep is driven sinusoidally in time while the vertical axis follows the signal amplitude. The analysis is aimed at determining the logarithmic derivative of the amplitude as a function of time. Within the Bayesian framework used, inferences are obtained with the Markov Chain Monte Carlo technique, which produces random samples from the posterior probability distribution expressed in terms of the parameters. [ABSTRACT FROM AUTHOR]

Published
2001

24. Gradient-based iterative image reconstruction scheme for time-resolved optical tomography

Author

Hielscher, Andreas, Klose, Alexander D., and Hanson, Kenneth M.

Subjects
Optical tomography -- Research, Infrared imaging -- Research, Diagnostic imaging -- Research, Business, Electronics, Electronics and electrical industries, Health care industry
Abstract

Currently available tomographic image reconstruction schemes for optical tomography (OT) are mostly based on the limiting assumptions of small perturbations and a priori knowledge of the optical properties of a reference medium. Furthermore, these algorithms usually require the inversion of large, full, ill-conditioned Jacobian matrixes. In this work a gradient-based iterative image reconstruction (GIIR) method is presented that promises to overcome current limitations. The code consists of three major parts: 1) A finite-difference, time-resolved, diffusion forward model is used to predict detector readings based on the spatial distribution of optical properties; 2) An objective function that describes the difference between predicted and measured data; 3) An updating method that uses the gradient of the objective function in a line minimization scheme to provide subsequent guesses of the spatial distribution of the optical properties for the forward model. The reconstruction of these properties is completed, once a minimum of this objective function is found. After a presentation of the mathematical background, two- and three-dimensional reconstruction of simple heterogeneous media as well as the clinically relevant example of ventricular bleeding in the brain are discussed. Numerical studies suggest that intraventricular hemorrhages can be detected using the GIIR technique, even in the presence of a heterogeneous background. Index Terms - Infrared imaging, optical tomography, time-resolved imaging, tomographic reconstruction, turbid media.

Published
1999

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