Search results for "Calibration"

Calibration of the Solar-B x-ray optics

2005

The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. XRT, designed for full sun imaging over the wavelength 6-60 Angstroms, will be the highest resolution solar X-Ray telescope ever flown. Images will be recorded by a 2048 X 2048 back-illuminated CCD with 13.5 μm pixels (1 arc-sec/pixel ) with full sun field of view. XRT will have a wide temperature sensitivity in order to observe and discriminate both the high (5-10 MK) and low temperature (1-5 MK) phenomena in the coronal plasma. This paper presents preliminary results of the XRT mirror calibration performed at the X-ray Calibration Facility, NASA-MSFC,…

The filter wheel and filters development for the X-IFU instruments onboard Athena

2016

Athena is the large mission selected by ESA in 2013 to investigate the science theme “Hot and Energetic Universe” and presently scheduled for launch in 2028. One of the two instruments located at the focus of the 12 m-long Athena telescope is the X-ray Integral Field Unit (X-IFU). This is an array of TES microcalorimeters that will be operated at temperatures of 50 mK in order to perform high resolution spectroscopy with an energy resolution down to 2.5 eV at energies < 7 keV. In order to cope with the large dynamical range of X-ray fluxes spanned by the celestial objects Athena will be observing, the X-IFU will be equipped with a filter wheel. This will allow the user to fine tune the i…

Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brachytherapy dosimetry

2015

Purpose: A surface electronic brachytherapy (EBT) device is in fact an x-ray source collimated with specific applicators. Low-energy (<100 kVp) x-ray beam dosimetry faces several challenges that need to be addressed. A number of calibration protocols have been published for x-ray beam dosimetry. The media in which measurements are performed are the fundamental difference between them. The aim of this study was to evaluate the surface dose rate of a low-energy x-ray source with small field applicators using different calibration standards and different small-volume ionization chambers, comparing the values and uncertainties of each methodology. Methods: The surface dose rate of the EBT unit …

Response to “Comment on ‘Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brac…

2016

The on-board calibration system of the X-ray Imaging Polarimetry Explorer (XIPE)

2016

The calibration system for XIPE is aimed at providing a way to check and correct possible variations of performance of the Gas Pixel Detector during the three years of operation in orbit (plus two years of possible extended operation), while facilitating the observation of the celestial sources. This will be performed by using a filter wheel with a large heritage having a set of positions for the calibration and the observation systems. In particular, it will allow for correcting possible gain variation, for measuring the modulation factor using a polarized source, for removing non interesting bright sources in the field of view and for observing very bright celestial sources. The on-board …

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

2013

This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Triggerrate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are …

A Study on the Measurement Instrumentation for a Custom-Made Bipendulum Impact Testing Machine

2008

Experimental investigations of structures under impact loads are normally carried out by means of drop-weight testing rigs, which are often tailor made, and require sensors for fast transient measurement of mechanical quantities (namely, force, displacement, velocity, and absorbed energy). Since these tests are quite expensive, time consuming, and, often, not repeatable, the sensors must provide reliable and interpretable results in the first trial. In this paper, a thorough study on the measurement instrumentation suitable to carry out reliable low-velocity impact tests by means of a custom-made bipendulum impact testing machine is presented. Attention has been focused on the choice of the…

Leveraging Uncertainty Estimates to Improve Segmentation Performance in Cardiac MR

2021

In medical image segmentation, several studies have used Bayesian neural networks to segment and quantify the uncertainty of the images. These studies show that there might be an increased epistemic uncertainty in areas where there are semantically and visually challenging pixels. The uncertain areas of the image can be of a great interest as they can possibly indicate the regions of incorrect segmentation. To leverage the uncertainty information, we propose a segmentation model that incorporates the uncertainty into its learning process. Firstly, we generate the uncertainty estimate (sample variance) using Monte-Carlo dropout during training. Then we incorporate it into the loss function t…

Spatial analysis of the homogeneity of the land surface temperature in three Spanish test sites

2015

Calibration and validation cal/val are key activities to test the data quality acquired from satellite-based instruments, as well as to report the accuracy of derived products such as the land surface temperature LST. Calibration of thermal infrared TIR data and validation of LST products at low spatial resolution requires the identification of large and homogeneous areas, which is a difficult task. In this work, spatial and temporal homogeneity of LST was analysed over three Spanish regions: the agricultural area of Barrax, Donana National Park, and Cabo de Gata Natural Park. For this purpose, very high spatial resolution approximately 3 m imagery acquired with the Airborne Hyperspectral S…

Smartphone determination of fat in cured meat products

2017

Abstract A method has been developed to determine the fat content in different cold meat products by image processing using the camera of a mobile phone. Salchichon , chorizo , salami and cured ham pictures were taken with a Meizu M2 Mini mobile phone camera under fixed lighting conditions of the light emitting diode flash of the mobile phone. Images were treated with Matlab to obtain the mean pixels of average red, green and blue camera values colours (RGB) of the pixels and different data pretreatments were taken into account to correlate colour parameters with fat content values determined in a series of commercially available samples by the Soxhlet method. RGB values were used as input …