Let X be an algebraic variety over the algebraically closed field K and Ξ ⊆ X(K) a set of K-rational points on X. We say that a subvariety Y ⊆ Xn of some Cartesian power of X is Ξ-special if Ξn ∩ Y (K) is Zariski dense in Y . We show under certain hypotheses on Ξ, for instance, that the class of Ξ-special varieties is closed under intersections, that when subvarieties of X vary in an algebraic ...

Raw output data from image sensors tends to exhibit a form of bias due to slight on-die variations between photodetectors, as well as between amplifiers. The resulting bias, called fixed pattern noise (FPN), is often corrected by subtracting its value, estimated through calibration, from the sensor’s raw signal. This paper introduces an online scene-based technique for an improved fixed-pattern...

In this paper, we use the recently presented wavelet-FFT filter [1] to reduce the nonuniformity noise that affect almost all infrared imaging systems. The wavelet-FFT filter was originally developed to compensate the onedimensional noise known as stripping noise. We perform an extension of this methodology in order to compensate the two-dimensional noise that degrades infrared imagery. The prin...

This paper describes a model for gain and offset non-uniformities and correction algorithm for nonuniformities. The infrared sensor model determines the number of photoelectrons generated from total incident flux and relates these electrons with integration time. It includes gain and offset non-uniformities in infrared sensor. A methodology for calibrating the sensor non-uniformities is present...

The specialised radiofrequency (RF) coils used in MRI such as head or surface coils can give rise to marked image intensity nonuniformities. There are two situations in which it is essential to correct this: (1) When a global intensity threshold is used to segment particular tissues; and (2) in proton density images, from which the proton concentration can be measured provided that the system g...

PURPOSE To develop a novel approach for calculating the accurate sensitivity profiles of phased-array coils, resulting in correction of nonuniform intensity in parallel MRI. MATERIALS AND METHODS The proposed intensity-correction method estimates the accurate sensitivity profile of each channel of the phased-array coil. The sensitivity profile is estimated by fitting a nonlinear curve to ever...