Transillumination imaging performance using time domain data

Light propagation in highly scattering media can be numerically simulated by solving the diffusion equation by the finite element method (FEM). Employing an iterative algorithm, the FEM solution of the forward problem is applied to the inverse imaging problem. Good test results were previously achieved when absorbers were searched in different objects. Now the reconstruction of scattering is also taken into account. Simulated measurement data are used to test and evaluate the method at various objects with tissue-like properties. Resulting problems are very ill posed. The algorithm is specially adapted to the illposedness of the problem. Improvements in reconstruction results can be achieved in two ways, first by adapting the detector arrangements and, secondly, by using a regularization strategy. The effectiveness of these methods is demonstrated by instructive examples

Simulation of maneuvering aircraft

Within the DLR-Project SikMa-„Simulation komplexer Manöver“ („Simulation of Complex Maneuvers“) the development of a numerical simulation framework for calculating a free flying aeroelastic manoeuvring combat aircraft is realised. To achieve this objective a multidisciplinary time accurate coupling of computational codes is done. The computational aerodynamic, structural and flight mechanic codes are embedded into an interactive simulation environment in which the coupling, data transfer, pre- and post-processing is done. On the CFD side the DLR TAU-Code is used to predict the unsteady aerodynamics. During the last year several project specific changes have been implemented in the TAU-Code. For calculating a fully equipped X-31, and coupling with the other disciplines, the handling of multi-body configurations and resulting motion definitions had to be enhanced, with regards to both the data exchange interface and the parallelization of the ADT search algorithm for the chimera overset grid technique. In order to calculate the deformation of the aircraft a CSM-Code is implemented in the simulation environment. The CSM-Code uses the full mass- and stiffness matrices of the given finite-element model, and has several interpolation routines for data-transfer between CFD and FEM grids; time-integration is done using an implicit Newmark algorithm. The DLR flight-mechanic library SIMULA is used to determine the flight trajectory of the free-flying, maneuvering aircraft. Wind tunnel experiments are provided in order to validate the simulation environment. The model used for the experiments is the X-31 configuration. The X-31 wind tunnel model is depicted in Fig. 1. The time accurate maneuver simulation of the X-31 will be shown. The simulation will start with the determination of a trim condition and than a maneuver due to control device deflectionwill be initiated. In a second simulation the structural mechanics behavior of the aircraft is also taken into account

Grundlegende Untersuchungen zur optischen Tomographie. Mathematische Behandlung der Streulichttomographie von dicken Gewebeschichten und Phantomen Abschlussbericht

Available from TIB Hannover: F98B102+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Optical imaging: 3D approximation and perturbation approaches for time-domain data

The reconstruction method presented here is based on the diffusion approximation for the light propagation in turbid media and on a minimization strategy for the output-least-squares problem. A perturbation approach is introduced for the optical properties. Here, the number of free variables of the inverse problem can be strongly reduced by exploiting a priori information such as the search for single inhomogeneities with a relatively homogeneous object, a typical situation for breast cancer detection. Higher accuracy and a considerable reduction of the computational effort are achieved by solving a parabolic differential equation for a perturbation density, i.e. the difference between the photon density in an inhomogeneous object and the density in the homogeneous case being given by an analytic expression. The calculations are performed by a 2D FEM algorithm, however, as a time-dependent correction factor is applied, the 3D situation is well approximated. The method was successfully tested by the University of Pennsylvania standard data set. Data noise was generated and taken into account in a modified data set. The influence of different noise on the reconstruction results is discussed. (orig.)Available from TIB Hannover: RR 5549(427)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman