arXiv subjects

D. Simicic

Publications and source records attributed to D. Simicic.

3 recordsLinked to original sources

arXiv2024

A Digital Phantom for MR Spectroscopy Data Simulation

Simulated data is increasingly valued by researchers for validating MRS processing and analysis algorithms. However, there is no consensus on the optimal approaches for simulation models and parameters. This study introduces a novel MRS digital brain phantom framework, providing a comprehensive and modular foundation for MRS data simulation. The framework generates a digital brain phantom by combining anatomical and tissue label information with metabolite data from the literature. This phantom contains all necessary information for simulating spectral data. The MRS phantom is combined with a signal-based model to demonstrate its functionality and usability in generating various spectral datasets. Outputs can be saved in the NIfTI-MRS format, enabling their use in downstream applications. To evaluate the realism of the simulated spectra, a comparison was performed against in-vivo MRS data acquired under similar conditions. The phantom was implemented using two anatomical templates at different resolutions and tested across a range of user-defined simulation parameters. Simulated spectra exhibited realistic signal characteristics and structural variability. When compared to in-vivo data, the simulated spectra closely matched in terms of spectral shape, signal-to-noise ratio, and metabolite quantification. The simulations also captured key variability features and provided additional diversity not present in the in-vivo dataset, supporting use in robustness testing and data augmentation. This novel digital phantom provides a flexible and extensible platform for MRS data simulation. Its modular architecture, user-friendly GUI, and open-source implementation support reproducible research, algorithm development, and validation in the MRS community.

physics.med-ph↗

arXiv2016

Developing a Launch Package for the PEGASUS Launcher

Railguns are capable to far exceed the muzzle energies of current naval deck guns. Therefore one of the most promising scenario for the future application of railguns in naval warfare is the long range artillery. Hypervelocity projectiles being propelled to velocities above 2 km/s reach targets at distances of 200 km or more. At the French-German Research Institute the PEGASUS launcher is used for investigations with respect to this scenario. The 6 m long barrel has a square caliber of 40 mm. The power supply unit is able to deliver 10 MJ to the gun. Within this investigation, a complete launch package is being developed and experiments are performed that aim at showing that this package can be accelerated to velocities ranging from 2000 m/s to 2500 m/s. A launch package consists out of an armature, a sabot and the projectile. The armature ensures the electrical contact during launch and pushes the sabot with its payload through the barrel. The sabot guides and protects the payload during the acceleration. At the same time the accelerating forces generated at the armature needs to be transferred to the projectile. After the launch package has left the barrel, the sabot should open and release its payload, the projectile into free-flight. Here the current status of the launch package development and results from experiments with the PEGASUS railgun are presented.

physics.plasm-ph↗

arXiv2016

Increasing Launch Efficiency with the PEGASUS Launcher

In the real world application of railguns, the launch efficiency is one of the most important parameters. This efficiency directly relates to the capacity of the electrical energy storage that is needed for the launch. In this study, the rail/armature contact behavior for two different armature technologies was compared. To this end, experiments using aluminum c-shaped armature and copper brush armature type projectiles were performed under same initial conditions. The c-shaped armature type showed a superior behavior with respect to electrical contact to the rails and in acceleration. A 300 g projectile with a c-shaped armature reached a velocity of 3100 m/s and an overall launch efficiency including the power supply of 41%. This is to be compared to 2500 m/s and 23% for the launching of a projectile using a brush armature.

physics.ins-det↗