Search NASA⌕ Search

Engineering topics

O'Connor, Daniel

Publications and source records attributed to O'Connor, Daniel.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Robust optimization for intensity-modulated proton therapy with soft spot sensitivity regularization

In this work, we developed a novel computationally efficient robust optimization method for IMPT. The robustness is calculated as the spot sensitivity to both range and shift perturbations. The dose fidelity term is then regularized by the sensitivity term for the flexibility and trade-off between the dosimetry and the robustness. In the stress test, SenR is more resilient to unexpected uncertainties. These advantages in combination with its fast computation time make it a viable candidate for clinical IMPT planning.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1992

Volcanic activity on Io at the time of the Ulysses encounter

The population of heavy ions in Io's torus is ultimately derived from Io volcanism. Ground-based infrared observations of Io between October 1991 and March 1992, contemporaneous with the 8 February 1992 Ulysses observations of the Io torus, show that volcanic thermal emission was at the low end of the normal range at all Io longitudes during this period. In particular, the dominant hot spot Loki was quiescent. Resolved images show that there were at least four hot spots on Io's Jupiter-facing hemisphere, including Loki and a long-lived spot on the leading hemisphere (Kanehekili), of comparable 3.5-micrometer brightness but higher temperature.

Spencer, John R.↗