2,064,746 research outputs found
CAMERA – Mobility Report 1
No full textThis report is a result of research performed so far in the scope of the CAMERA Coordination and Support Action (CSA). In CAMERA, we investigate research initiatives from the past decade that focus on the European air transport system and its integration with other transport modes, with a special focus on addressing the customer experience and point of view. The focus of this report is the review of the research under FP7 and its successor, H2020, as these have supported a large number of research activities in air mobility in the last decade. Its objective is to analyse 158 selected research initiatives in European mobility research to determine their coverage of mobility challenges, identify potential gaps and form recommendations for future research initiatives. This is the first of four Annual Mobility Reports that CAMERA is planning to publish. It outlines the initial findings and describes the future efforts of this Coordination and Support Action
Domenico Camera - Scritti d'arte
No full textPresentazione di Domenico Camera, un "poeta prestato all'arte", già oggetto di attenzione critica da parte di illustri studiosi della letteratura italiana contemporanea, tra cui Franco Contorbia
Invoking Voids in the Archive
No full textThis is the author accepted manuscript. The final version is available from Camera Austria via the DOI in this recor
Optimizing Compton camera performance
No full textAmore realistic simulation approach is used to study the behavior of the Compton camera in
this thesis than previous studies to date. The Compton camera differs from gamma cameras
in that the collimator is replaced by a detector known as the ‘scatterer’. Gamma rays may be
Compton scattered in the scatterer and subsequently detected by an ‘absorber’ which is the
equivalent of the detector in a gamma camera. By measuring the energies and the positions
of the points on the scatterer and the absorber where the incident and scattered gamma rays
interacted with the detectors, an image of the source can be reconstructed. Because there is
no collimator present, the potential sensitivity of the Compton camera is much higher than
the gamma camera, resulting in reduced acquisition times.
Most of the work described in this thesis was done with the GEANT4 Monte Carlo
simulation software. GEANT4 has been proven to be very robust and efficient in modelling
physics problems of radiation transport and interactions with matter in complex geometries.
Four major studies are carried out to estimate and optimize the performance of this
novel equipment. The first study takes a look at the scatterer’s imaging parameters with
the aim of prescribing an optimal scatterer material and geometry. In the second study,
the contribution of the absorber to the overall Compton camera performance is evaluated,
considering detector material, interaction type and geometry. The third study explores the
limitations imposed by the detector energy threshold and dead time on the Compton camera
performance, using a simplified model of the general electronic architecture. An evaluation
of Compton camera for scintimammography was performed in the fourth study. For
this study, three dual-head Compton camera models (Si/CZT, Si/LaBr₃:Ce and Si/NaI(Tl)
Compton cameras) were simulated, and the effect of scintillation photons’ interactions with
the photomultipliers was implemented.
The results show that silicon of about 1 cm thickness would be adequate as the Compton
camera scatterer. Analyses suggest however, that the choice of silicon is not completely
flawless. Doppler broadening for this detector material contributes as much as 7.3 mm
and 2.4 mm to full-width-at-half-maximum (FWHM) image resolution at 140.5 keV and
511 keV respectively. On the other hand, detector spatial resolution which accounts for
the least image degradation at 140.5 keV is found to be the dominant degrading factor
at 511 keV, suggesting that the absorber parameters play major roles in image resolution
at higher diagnostic energies. Findings further suggest that cadmium zinc telluride (CZT)
would be themost suitable detector as the absorber since thematerial demonstrated the highest efficiency and least positioning error due to multiple interactions as well as good spatial
resolution. The inclusion of the energy threshold and detector dead time at 140.5 keV, reduced
the Compton camera detection efficiency by 48% and 17% respectively, but improved
the image resolution from 10.7 mm to 9.5 mm at the source-to-scatterer distance of 5 cm.
At 511 keV, the inclusion of these parameters reduced the efficiency by 6% and 13% respectively,
but made no significant difference on the camera resolution. For a challenging
detection case in scintimammography, 5 mm breast tumours of tumour/background uptakes
of 10:1 and 6:1 at 511 keV were used. The best signal-to-noise ratio (SNR) was attained
for the Si/CZT Compton camera model, with the SNR values of 12.2 and 5.3.
It is therefore envisioned that with an optimal camera geometry, improved reconstruction
technique and adequate filter algorithm, the combination of Si and CZT as the scatterer
and the absorber of the Compton camera would make a very promising imaging system for
nuclear medicine studies at higher gamma ray energies where the collimated SPECT systems
perform very poorly due to increased septal penetration. It is equally evident from the
studies that with improved technology, new detectors such as LaBr₃:Ce could replace the
traditional NaI(Tl) detector as imaging detectors
More Accurate Pinhole Camera Calibration with Imperfect Planar Target
No full textThis paper presents a novel approach to camera calibration that improves final accuracy with respect to standard methods using precision planar targets, even if now inaccurate, unmeasured, roughly planar targets can be used. The work builds on a recent trend in camera calibration, namely concurrent optimization of scene structure together with the intrinsic camera parameters. A novel formulation is presented that allows maximum likelihood estimation in the case of inaccurate targets, as it extends the camera extrinsic parameters into a tight parametrization of the whole scene structure. It furthermore observes the special characteristics of multi-view perspective projection of planar targets. Its natural extensions to stereo camera calibration and hand-eye calibration are also presented. Experiments demonstrate improvements in the parametrization of the camera model as well as in eventual stereo reconstruction
Durham All-Sky Camera (DAC)
No full textIn this work, the prototype of a Durham all-sky camera (DAC) was designed and constructed for the purpose of monitoring the night sky of Durham. The DAC consisted of a Fujinon fish-eye lens coupled to a monochrome 640-by-480-pixel CCD camera (DMK-21BF04 model from the ImagingSource) housed in an 8-inch Perspex dome. After construction, the images were taken of the night sky in order to determine the properties of DAC. The field of view of the DAC was 185˚ at average scale of 0.2˚ per pixel.
The astrometric characteristics of the camera were investigated by measuring the relationship between star positions on the 3-D celestial hemisphere and their projected 2-D pixel positions on the DAC CCD images. The derived relationship (the mapping) of the stars onto the CCD images achieved an average uncertainty of 1 pixel. For the reverse process, the uncertainties were 0.2˚ in elevation and 0.7˚ in azimuth. The relationship was tested for the robustness and was found to be stable at the level of 1 pixel.
The photometric characteristics of the camera were studied by investigating how well the magnitude of a star could be measured by DAC. The results showed that, under the sky background condition in Durham, the camera was able to determine a 6th magnitude star at zenith within 1 magnitude uncertainty, but a 4th magnitude star within the similar uncertainty when the stars were at an elevation of 30˚. The brightness of the sky background of Durham was determined to be 18 magnitudes per square arcsecond. Subsequently, the comparison was drawn between the sky background in Durham and in Hawaii, thereby estimating that the accuracy of measuring a 6th magnitude star would be about 7 times better if the camera was deployed under the darker sky background of Hawaii
Notan, Bulletin of the Seattle Camera Club, No. 16, September 11, 1925
No full textIn Japanese and English.
Printed on cover: The Seattle Camera Club. 422 1/2 Main Street, Seattle, Washington. Editors: R. Azuma, Y.T. Iwasaki, S. Kashiwag1, K. Koike; Associate Editor: Glenn Hughes
Notan, Bulletin of the Seattle Camera Club, No. 29, October 8, 1926
No full textIn Japanese and English.
Printed on cover: The Seattle Camera Club. 422 1/2 Main Street, Seattle, Washington. Editors: R. Azuma, Y.T. Iwasaki, S. Kashiwagi, K. Koike; Associate Editor: Glenn Hughes
Notan, Bulletin of the Seattle Camera Club, No. 22, March 12, 1926
No full textIn Japanese and English.
Printed on cover: The Seattle Camera Club. 422 1/2 Main Street, Seattle, Washington. Editors: R. Azuma, Y.T. Iwasaki, S. Kashiwagi, K. Koike; Associate Editor: Glenn Hughes
Camera Self-Calibration for the ARToolkit
No full textCamera calibration is an essential and important part of an Augmented Reality (AR) system. The use of a planebased calibration technique can give a good accuracy, which can be important for AR applications. The calibration technique used in the current ARToolKit requires user intervention, which is prone to error and involves a lengthy calibration time. The camera has to be recalibrated every time the focal length changes which is cumbersome and less suitable for applications where a more automated and easier approach is needed. This paper investigates the use of camera self-calibration for the ARToolKit, which has the advantage of simplicity of implementation. In order to improve its accuracy, a distortion model is also investigated. In this context several interesting results are presented
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