Engineering topics
Zimmer, Robert
Publications and source records attributed to Zimmer, Robert.
Laboratory Performance of the Shaped Pupil Coronagraphic Architecture for the WFIRST-AFTA Coronagraph
One of the two primary architectures being tested for the WFIRST-AFTA coronagraph instrument is the shaped pupil coronagraph, which uses a binary aperture in a pupil plane to create localized regions of high contrast in a subsequent focal plane. The aperture shapes are determined by optimization, and can be designed to work in the presence of secondary obscurations and spiders-an important consideration for coronagraphy with WFIRSTAFTA. We present the current performance of the shaped pupil testbed, including the results of AFTA Milestone 2, in which approximately 6 × 10(exp −9) contrast was achieved in three independent runs starting from a neutral setting.
When Does Changing Representation Improve Problem-Solving Performance?
The aim of changing representation is the improvement of problem-solving efficiency. For the most widely studied family of methods of change of representation it is shown that the value of a single parameter, called the expulsion factor, is critical in determining (1) whether the change of representation will improve or degrade problem-solving efficiency and (2) whether the solutions produced using the change of representation will or will not be exponentially longer than the shortest solution. A method of computing the expansion factor for a given change of representation is sketched in general and described in detail for homomorphic changes of representation. The results are illustrated with homomorphic decompositions of the Towers of Hanoi problem.