May 7th, 2009| 11:14 am | Posted by hlee

One of [ArXiv] papers from yesterday whose title might drag lots of attentions from astronomers. Furthermore, it’s a short paper.

[arxiv:math.CO:0905.0483] by Harmany, Marcia, and Willet.

Continue reading ‘[ArXiv] Sparse Poisson Intensity Reconstruction Algorithms’ »

Tags:

compressed sensing,

decomposition,

EM algorithm,

intensity,

MPLE,

multiscale,

penalty,

Poisson,

Poisson Intensity,

Sparcity,

wavelet Category:

Algorithms,

arXiv,

Astro,

Cross-Cultural,

Data Processing,

High-Energy,

Imaging,

Jargon |

Comment
Dec 11th, 2008| 03:46 pm | Posted by hlee

A few scientists in our group work on estimating the intensities of gamma ray observations from sky surveys. This work distinguishes from typical image processing which mostly concerns the point estimation of intensity at each pixel location and the size of overall white noise type error. Often times you will notice from image processing that the orthogonality between errors and sources, and the white noise assumptions. These assumptions are typical features in image processing utilities and modules. On the other hand, CHASC scientists relate more general and broad statistical inference problems in estimating the intensity map, like intensity uncertainties at each point and the scientifically informative display of the intensity map with uncertainty according to the Poisson count model and constraints from physics and the instrument, where the field, **multiscale modeling** is associated. Continue reading ‘[MADS] multiscale modeling’ »

May 28th, 2008| 01:00 pm | Posted by vlk

The most widely used tool for detecting sources in X-ray images, especially Chandra data, is the wavelet-based `wavdetect`, which uses the Mexican Hat (MH) wavelet. Now, the MH is not a very popular choice among wavelet aficianados because it does not form an orthonormal basis set (i.e., scale information is not well separated), and does not have compact support (i.e., the function extends to inifinity). So why is it used here?

Continue reading ‘Mexican Hat [EotW]’ »

Tags:

Chandra,

ciao,

convolution,

correlation,

EotW,

Equation,

Equation of the Week,

Fourier Transform,

gaussian,

MexHat,

Mexican Hat,

MH,

multiscale,

wavdetect,

wavelet Category:

Algorithms,

Astro,

Imaging,

Jargon |

1 Comment
Apr 20th, 2008| 09:05 pm | Posted by hlee

The dichotomy of outliers; detecting outliers to be discarded or to be investigated; statistics that is robust enough not to be influenced by outliers or sensitive enough to alert the anomaly in the data distribution. Although not related, one paper about outliers made me to dwell on what outliers are. This week topics are diverse. Continue reading ‘[ArXiv] 3rd week, Apr. 2008’ »

Tags:

background,

bootstrap,

calibration errors,

Cash statistics,

clusters,

CMB,

corona,

edge detection,

FFT,

gravitational lens,

maximum likelihood,

multiscale,

neural network,

outlier,

SDSS,

sunspot,

systematic errors,

topology,

WMAP,

XMM-Newton Category:

arXiv,

High-Energy,

MCMC |

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