Search results for "RESOLUTION"
showing 10 items of 1928 documents
Relationship between resolution and accuracy of four intraoral scanners in complete-arch impressions
2018
Background The scanner does not measure the dental surface continually. Instead, it generates a point cloud, and these points are then joined to form the scanned object. This approximation will depend on the number of points generated (resolution), which can lead to low accuracy (trueness and precision) when fewer points are obtained. The purpose of this study is to determine the resolution of four intraoral digital imaging systems and to demonstrate the relationship between accuracy and resolution of the intraoral scanner in impressions of a complete dental arch. Material and methods A master cast of the complete maxillary arch was prepared with different dental preparations. Using four di…
Thermoelastic stress analysis by means of an infrared scanner and a two-dimensional fast Fourier transform-based lock-in technique
2008
An infrared thermographic experimental set-up has been proposed and evaluated towards the capability to measure thermoelastic-effect-induced temperature changes. A standard infrared thermocamera with a nominal noise-equivalent temperature difference (NETD) resolution of 0.12 K has been employed to measure the temperature from unidirectional glass-reinforced plastic tensile coupons under cyclic sinusoidal loads. The raster scanning mode of the camera single detector produces a time delay in acquiring the signal from two succeeding pixels on the same row, and from consecutive scanned rows. By exploiting the acquired dwell times, it was possible to produce a periodic pattern on the thermal ma…
19F-MRT der Lungenventilation in Atemanhaltetechnik mittels SF6-Gas
2000
Breathhold 19 F-Magnetic Resonance Imaging of Lung Ventilation using SF 6 Gas. Objective: Development of a method to analyze lung ventilation by 19 F-magnetic resonance imaging (MRI) of inspired SF 6 gas during breathhold. Material and Methods: Measurements were performed with a Siemens Magnetom Vision 1.5T scanner using the conventional gradient overdrive. Coronal images of the lung were acquired using ultrafast gradient-echo pulse sequences with TR/TE/α = 1.4 ms/ 0.48 ms/40° without slice selection. With NEX = 200 averages and MA = 32 × 64 raw data matrix, the acquisition time was 9s/image. Higher spatial resolution of 4.7 × 6.3 × 15 mm 3 was obtained with a three-dimensional pulse sequen…
How to Determine Reliable Intensities Using Film Methods?
1997
The basis of a successful structure analysis is to obtain reliable intensities. In the field of electron crystallography intensity data can be collected on-line with a CCD-camera as well as off-line using image plates or film material. Whereas image plates are read out with a laser, film material is analysed via a densitometer or digitised using a CCD-camera or a scanner. Both, CCD-camera and scanner, uses CCDtechnology and we show that both systems can be used for intensity evaluation. In order to obtain reliable intensities from film media it is important to define and calibrate the experimental conditions, the digitization process and the evaluation of intensity data exactly. A high opti…
A high-resolution PET demonstrator using a silicon "magnifying glass".
2021
Abstract To assist ongoing investigations of the limits of the tradeoff between spatial resolution and noise in PET imaging, several PET instruments based on silicon-pad detectors have been developed. The latest is a segment of a dual-ring device to demonstrate that excellent reconstructed image resolution can be achieved with a scanner that uses highresolution detectors placed close to the object of interest or surrounding a small field-of-view in combination with detectors having modest resolution at larger radius. The outer ring of our demonstrator comprises conventional BGO block detectors scavenged from a clinical PET scanner and located at a 500 mm radius around a 50 mm diameter field…
FLEX End-to-End Mission Performance Simulator
2016
The FLuorescence EXplorer (FLEX) mission, selected as the European Space Agency's eighth Earth Explorer, aims to globally measure the sun-induced-chlorophyll-fluorescence spectral emission from terrestrial vegetation. In the frame of the FLEX mission, several industrial and scientific studies have analyzed the instrument design, image processing algorithms, or modeling aspects. At the same time, a common tool is needed to address the overall FLEX mission performance by combining all these features. For this reason, an end-to-end mission performance simulator has been developed for the FLEX mission (FLEX-E). This paper describes the FLEX-E software design, which combines the generation of co…
Generalized wavelets design using Kernel methods. Application to signal processing
2013
Abstract Multiresolution representations of data are powerful tools in signal processing. In Harten’s framework, multiresolution transforms are defined by predicting finer resolution levels of information from coarser ones using an operator, called the prediction operator, and defining details (or wavelet coefficients) that are the difference between the exact values and the predicted values. In this paper we present a multiresolution scheme using local polynomial regression theory in order to design a more accurate prediction operator. The stability of the scheme is proved and the order of the method is calculated. Finally, some results are presented comparing our method with the classical…
Preparing Teachers for Teaching Probability Through Problem Solving
2018
In this paper we introduce the idea of solving problems by simulation with didactical intention. Based on this idea, we analyse the way we prepare the teachers to teach solving probability problems by simulation, in distinguishing whether the teaching is offered to prospective elementary teachers or secondary school teachers. The process of solving probability problems is seen as an inquiry process, which uses simulation as a resolution method with heuristic content, so that the preparation of teacher is then based on this approach. Therefore, prospective teachers should have the opportunities to learn about probability problems, about the process of solving probability problems, and about …
Gamma-ray position reconstruction in large lanthanum-halide crystals with SiPM readout: analytical vs. neural-network algorithms
2019
The main objective of this research was to achieve an excellent gamma-ray position reconstruction with very large monolithic scintillation crystals coupled to pixelated silicon photosensors. Analyzing the scintillation-light distribution measured along the SiPM-pixels one can get a sub-pixel accuracy for the position reconstruction. The quality of the latter depends on both the characteristics of the crystal-photosensor assembly, and the goodness of the algorithm used to reconstruct the gamma-ray hit location. We have carried out a systematic study for 511 keV gamma-rays using three different crystal thicknesses of 10 mm, 20 mm and 30 mm, all of them with planar geometry and a base size of …
<title>Surface temperature retrieval from MODIS data</title>
2001
12 MODIS (Moderate Resolution Imaging Spectroradiometer) was launched on board the NASA's Terra Earth Observing System (EOS AM-1) Satellite on December 18, 1999. We propose in this work operative split-window algorithms for retrieving sea surface temperature (SST) and land surface temperature (LST) using MODIS data. In order to attain our goal, the MODTRAN 3.5 radiative transfer code was used to predict radiances for MODIS channels 31 and 32. To analyze atmospheric effects, a set of radiosoundings was used to cover the variability of surface temperature and water vapor concentration on a worldwide scale. These simulated data were split into two sets which have very similar distributions in …