Kalman Filter Estimation for Focal Plane Wavefront Correction

Space-based coronagraphs for future earth-like planet detection will require focal plane wavefront control techniques to achieve the necessary contrast levels. These correction algorithms are iterative and the control methods require an estimate of the electric field at the science camera, which requires nearly all of the images taken for the correction. We demonstrate a Kalman filter estimator that uses prior knowledge to create the estimate of the electric field, dramatically reducing the number of exposures required to estimate the image plane electric field. In addition to a significant reduction in exposures, we discuss the relative merit of this algorithm to other estimation schemes, particularly in regard to estimate error and covariance. As part of the reduction in exposures we also discuss a novel approach to generating the diversity required for estimating the field in the image plane. This uses the stroke minimization control algorithm to choose the probe shapes on the deformable mirrors, adding a degree of optimality to the problem and once again reducing the total number of exposures required for correction. Choosing probe shapes has been largely unexplored up to this point and is critical to producing a well posed set of measurements for the estimate. Ultimately the filter will lead to an adaptive algorithm which can estimate physical parameters in the laboratory and optimize estimation.Comment: 14 pages, 9 figures, SPIE Astronomical Telescopes and Instrumentation 2012 conference proceedings. Journal version at arXiv:1301.382

Locke v. United States and the Definition of Probable Cause in U.S. Civil Forfeiture Proceedings

United States civil forfeiture laws are rooted in admiralty in rem forfeiture proceedings that go back to mid-1700s English customs law, and a statute called the Act of Frauds. The procedure was born of the necessity of international marine trade. Similarly, when it came to using in rem seizure to enforce the customs laws, the Crown used a burden shifting presumption that was also born of necessity. Vessel owners were required to come forward and exculpate their vessel once the Crown showed probable cause of a violation. In Locke v. United States, Justice Marshall upheld that burden shifting presumption and the definition of probable cause in the admiralty in rem seizure context as a showing of reasonable suspicion, something less than a prima facie case. Sixty years later, however, the United States courts would begin to uphold uses of in rem forfeiture outside of the context of customs law, and today, statutory forfeiture provisions are constitutional scholars question whether or not civil forfeiture proceedings, having entered the law in the narrow context of admiralty in rem forfeiture proceedings, do an end run around the Fourth Amendment and Due Process. The Locke Court never heard or considered any constitutional argument

Youth and conservation methods

How to get young people interested in conservation and environmental preservation is a concern for educators and environmental groups. One possibility explored here was to encourage students to speak with people who are carrying out agricultural conservation practices and then try to summarize these ideas and experiences in a videotape

Some Semantics of Basic Word Lists

Lists of words compiled on the basis of their frequency of occurrence in writings of various kinds have long been considered basic materials for reading instruction. It is said teachers should use such lists because the child best learns to read if the order of the words presented to him for this purpose is governed by the relative frequency words occur in written materials. Put another way, it is argued that if word A occurs more often in written matter of different types than does word B it then should be presented for a child to learn to read before word B is presented. There is a certain logic to support this procedure. Unknown words that appear frequently in a child\u27s reading material surely pose more of a handicap to his success here than would unknown words that appear infrequently. Consequently, one can agree with Hillerich1 that most educators accept the need for a basic list

Children\u27s Recognition of Words in Isolation and in Context

The extent to which young children use, or should use sentence contexts as cues to word recognition is an unsettled issue. It is clear, on the one hand, that there are inherent limitations in this cue system to its successful use for this purpose (Groff, 1975). Also, the notion that beginning readers have little else on which to rely for word recognition except context cues, as offered by Karlin (1971, p. 145) has also been demonstrated as false. To the contrary, the research on word recognition suggests that these young children use letters as the main cues for word recognition from the time they first begin to learn to read (Groff, 1974)

Making Their Voices Count: Using Students’ Perspectives to Inform Literacy Instruction for Striving Middle Grade Readers with Academic Difficulties

The consequences of lack of reading and poor reading skills are problematic for all students, regardless of background; however, for middle grade striving readers with academic difficulties these problems can lead to lower self-efficacy and motivation to engage in literacy tasks. Using the perspectives of urban, middle grade special education students, this article seeks to demonstrate how teachers can use student interview feedback to differentiate instruction by aligning their voices with appropriate practices. Consistent with previous research, (Roe, 2009; Smith &Wilhelm, 2002), the data show that supportive contexts increase self-efficacy and interest in reading. These perspectives have the potential to provide teachers with better insight about the needs of striving middle grade readers and inform their instructional strategies and materials