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Apr 21 2015

A neural net A-vector estimator?

Tag: Uncategorized — admin @ 12:25 pm
Recently, Zimmerman and Schmidt published a paper[4] comparing the A-table estimator to a neural net estimator. Their main purpose was to compare the estimators with their experimental data but they did mention that they compared the estimators with a simulation. With this, they stated that “Both the neural network and A-table methods demonstrated a similar performance for the simulated data.” This interested me so I decided to compare the estimators using my simulation software to see if I could replicate their results. However, I found that, although the neural network estimator does a great job on no-noise data, with noise it has a substantially larger (about a factor of 100) variance and mean squared error than the A-table estimator. I also compared the estimators with the synthesized attenuation coefficient measure suggested by Zimmerman and Schmidt and found the neural net had about a factor of 10 larger value, which is consistent with the variance results. I am puzzled about the difference in the results here and Zimmerman and Schmidt’s but the code for this post can be used to reproduce the results so any errors or discrepancies can be tracked down.

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Oct 29 2011

Deadtime 4-Monte Carlo simulation of PHA data

Tag: Implementation,Noise,Physics,Uncategorized — admin @ 10:22 am

I used a Monte Carlo simulation to test the formulas derived in my last post for the mean value, variance, and covariance of pulse height analysis (PHA) data as a function of deadtime. In this post, I discuss the simulation software and the results. The formulas were quite accurate except for the covariance where the relatively small value and the difficulty in getting good statistics for variance estimates in general caused a spread around the theoretical values.

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Apr 28 2011

Welcome

Tag: Uncategorized — admin @ 3:20 pm

The main theme of this blog is energy selective x-ray images. My approach is to combine theoretical and mathematical topics with code to implement them and examples of their use.

A free ebook on these topics is available. To get it, email me at the address on the contact page

I have turned off the comments because of spam. If you want to comment, send an email at the Contact.

Here is a map of some topics that I want to cover. I made it using ithoughtsHD on an Ipad, Freemind and Seamonkey on the PC (more on those in later posts)

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