Refine
Year of publication
- 2005 (303) (remove)
Institute
- Fachbereich Medizintechnik und Technomathematik (48)
- Fachbereich Maschinenbau und Mechatronik (43)
- Fachbereich Luft- und Raumfahrttechnik (41)
- Fachbereich Energietechnik (39)
- Fachbereich Wirtschaftswissenschaften (29)
- Fachbereich Elektrotechnik und Informationstechnik (25)
- IfB - Institut für Bioengineering (24)
- Fachbereich Chemie und Biotechnologie (20)
- Fachbereich Bauingenieurwesen (18)
- INB - Institut für Nano- und Biotechnologien (17)
Language
- German (170)
- English (130)
- Portuguese (2)
- Spanish (1)
Document Type
- Article (188)
- Conference Proceeding (37)
- Book (30)
- Lecture (18)
- Part of a Book (12)
- Patent (6)
- Other (3)
- Part of a Periodical (3)
- Doctoral Thesis (2)
- Diploma Thesis (1)
Keywords
- Rapid Prototyping (6)
- Übungsklausur (5)
- Aachen University of Applied Sciences (3)
- Bauingenieurwesen (3)
- CAD (3)
- Fachhochschule Aachen (3)
- Fertigungsverfahren (3)
- Regelungstechnik (3)
- civil engineering (3)
- Karosseriebau (2)
The optical properties of the thin metalized polymer films that are projected for solar sails are assumed to be affected by the erosive effects of the space environment. Their degradation behavior in the real space environment, however, is to a considerable degree indefinite, because initial ground test results are controversial and relevant inspace tests have not been made so far. The standard optical solar sail models that are currently used for trajectory design do not take optical degradation into account, hence its potential effects on trajectory design have not been investigated so far. Nevertheless, optical degradation is important for high-fidelity solar sail mission design, because it decreases both the magnitude of the solar radiation pressure force acting on the sail and also the sail control authority. Therefore, we propose a simple parametric optical solar sail degradation model that describes the variation of the sail film’s optical coefficients with time, depending on the sail film’s environmental history, i.e., the radiation dose. The primary intention of our model is not to describe the exact behavior of specific film-coating combinations in the real space environment, but to provide a more general parametric framework for describing the general optical degradation behavior of solar sails. Using our model, the effects of different optical degradation behaviors on trajectory design are investigated for various exemplary missions.
Mit Logik die Welt begreifen
(2005)
Stahlbau
(2005)
Formeln statt Zahlen : Referenzwerte Formeln zur energetischen Bewertung von Produktionsanlagen
(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.
The ClearPET™ project: Development of a 2nd generation high-performance small animal PET scanner
(2005)
Second generation high-performance PET scanners, called ClearPET™1, have been developed by working groups of the Crystal Clear Collaboration (CCC). High sensitivity and high spatial resolution for the ClearPET camera is achieved by using a phoswich arrangement combining two different types of lutetium-based scintillator materials: LSO from CTI and LuYAP:Ce from the CCC (ISTC project). In a first ClearPET prototype, phoswich arrangements of 8×8 crystals of 2×2×10 mm3 are coupled to multi-channel photomultiplier tubes (Hamamatsu R7600). A unit of four PMTs arranged in-line represents one of 20 sectors of the ring design. The opening diameter of the ring is 120 mm, the axial detector length is 110 mm.The PMT pulses are digitized by free-running ADCs and digital data processing determines the gamma energy, the phoswich layer and even the exact pulse starting time, which is subsequently used for coincidence detection. The gantry allows rotation of the detector modules around the field of view.
Preliminary data shows a correct identification of the crystal layer about (98±1)%. Typically the energy resolution is (23.3±0.5)% for the luyap layer and (15.4±0.4)% for the lso layer. early studies showed the timing resolution of 2 ns FWHM and 4.8 ns FWTM. the intrinsic spatial resolution ranges from 1.37 mm to 1.61 mm full-width of half-maximum (FWHM) with a mean of 1.48 mm FWHM. further improvements in image and energy resolution are expected when the system geometry is fully modeled.