Article
Refine
Year of publication
- 2005 (99) (remove)
Institute
- Fachbereich Medizintechnik und Technomathematik (36)
- Fachbereich Luft- und Raumfahrttechnik (21)
- IfB - Institut für Bioengineering (21)
- INB - Institut für Nano- und Biotechnologien (15)
- Fachbereich Elektrotechnik und Informationstechnik (13)
- Fachbereich Chemie und Biotechnologie (10)
- Fachbereich Energietechnik (7)
- Fachbereich Maschinenbau und Mechatronik (5)
- Freshman Institute (4)
- Fachbereich Architektur (1)
Language
- English (99) (remove)
Document Type
- Article (99) (remove)
Keywords
- Alternating plasticity (1)
- Analytischer Zulaessigkeitsnachweis (1)
- Axialbelastung (1)
- Axially cracked pipe (1)
- Deformation (1)
- Design-by-analysis (1)
- Einspiel-Analyse (1)
- Einspiel-Kriterium (1)
- Einspielen <Werkstoff> (1)
- FEM (1)
- Finite-Elemente-Methode (1)
- Global and local collapse (1)
- Grenzwertberechnung (1)
- Limit analysis (1)
- Plastizität (1)
- Pressure loaded crack-face (1)
- Progressive plastic deformation (1)
- Shakedown analysis (1)
- Shakedown criterion (1)
- Traglastanalyse (1)
- alternierend Verformbarkeit (1)
- fortschreitende plastische Deformation (1)
The ClearPET® scanners developed by the Crystal Clear Collaboration use multichannel PMTs as photodetectors with scintillator pixels coupled individually to each channel. In order to localize an event each channel anode is connected to a comparator that triggers when the anode signal exceeds a common predefined threshold. Two major difficulties here are crosstalk of light and the gain nonuniformity of the PMT channels. Crosstalk can generate false triggering in channels adjacent to the actual event. On the one hand this can be suppressed by sufficiently increasing the threshold, but on the other hand a threshold too high can already prevent valid events on the lower gain channels from being detected. Finally, both effects restrict the dynamic range of pulse heights that can be processed. The requirements to the dynamic range are not low as the ClearPET® scanners detect the depth of interaction by phoswich pixels consisting of LSO and Lu0.7Y0.3AP, two scintillators with different light yields. We will present a model to estimate the achievable dynamic range and show solutions to increase it.
Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. FEM suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to FEM limit analyses for all crack dimensions.
In the new European standard for unfired pressure vessels, EN 13445-3, there are two approaches for carrying out a Design-by-Analysis that cover both the stress categorization method (Annex C) and the direct route method (Annex B) for a check against global plastic deformation and against progressive plastic deformation. This paper presents the direct route in the language of limit and shakedown analysis. This approach leads to an optimization problem. Its solution with Finite Element Analysis is demonstrated for mechanical and thermal actions. One observation from the examples is that the so-called 3f (3Sm) criterion fails to be a reliable check against progressive plastic deformation. Precise conditions are given, which greatly restrict the applicability of the 3f criterion.
Miniaturised reference electrodes for field-effect sensors compatible to silicon chip technology
(2005)
468 Scatter dose determination at the eye lens during a mask based whole brain radiotherapy (WBRT)
(2005)
This study has been performed to design the combination of the new ClearPET (ClearPET is a trademark of the Crystal Clear Collaboration), a small animal positron emission tomography (PET) system, with a micro-computed tomography (microCT) scanner. The properties of different microCT systems have been determined by simulations based on GEANT4. We will demonstrate the influence of the detector material and the X-ray spectrum on the obtained contrast. Four different detector materials (selenium, cadmium zinc telluride, cesium iodide and gadolinium oxysulfide) and two X-ray spectra (a molybdenum and a tungsten source) have been considered. The spectra have also been modified by aluminum filters of varying thickness. The contrast between different tissue types (water, air, brain, bone and fat) has been simulated by using a suitable phantom. The results indicate the possibility to improve the image contrast in microCT by an optimized combination of the X-ray source and detector material.