The PMSS approach to large-scale optimal control problems

Large-scale optimal control problems arise in several different contexts from a variety of applications. Many general computational algorithms have been proposed for the solution of these problems and a large literature on the subject abounds. To assimilate this material, it is necessary to overcome several difficulties. For example, the large-scale nature of the problems induces a complicated notation and specialized jargon that sometimes confuses the basic issues. Further, the ad hoc nature of the development of many algorithms tends to add an air of mystery that is difficult to dispel. Consequently, it is not always apparent that there are simple concepts and principles that underlie most, if not all, of these algorithms. In this paper, the general taxonomic scheme proposed by Geoffrion is exploited to provide a systematic framework for viewing computational algorithms for solving large-scale, optimal control problems. To demonstrate the utility of the viewpoint, a new algorithm for solving large-scale, discrete-time nonlinear optimal control problems is presented. The development is directed by the simple concepts and principles that underlie the proposed taxonomy.     

A method for aligning trans-tibial residual limb shapes so as to identify regions of shape change.

Quantification of the change in shape of a residual limb over time is relevant to the fitting of an external prosthesis. Three algorithms were developed and evaluated to align residual limb shapes: iterative closest points (ICP), mean absolute difference, and weighted surface normals/mean absolute difference. Evaluations were conducted by aligning residual limb shapes with known deformations and transformations with their original shapes. Results showed that ICP did not perform well in that it tended to favor a global distribution of local shape difference rather than localization of the error. The mean absolute difference algorithm performed well as long as the shape difference was localized to one region. Weighted mean surface normals/absolute difference provided the best alignment results, performing well both if shape changes were localized and if they were globally distributed. Mean alignment errors for this method were less than 0.285 mm for each of the three translation directions and less than 0.357 degrees for each of the three rotation directions. This algorithm could be helpful to patients, prosthetists, and researchers developing treatments to overcome the detrimental fitting effects of residual limb shape change.     

Ammunition is the principal source of lead accumulated by California condors re-introduced to the wild

The endangered California Condor (Gymnogyps californianus) was reduced to a total population of 22 birds by the end of 1982. Their captive-bred descendants are now being released back into the wild in California, Arizona, and Baja California, where monitoring indicates they may accumulate lead to toxic levels. Fragments of ammunition in the carcasses of game animals such as deer, elk, and feral pigs not retrieved by hunters or in gut piles left in the field have been considered a plausible source of the lead, though little direct evidence is available to support this hypothesis. Here, we measured lead concentrations and isotope ratios in blood from 18 condors living in the wild in central California, in 8 pre-release birds, and in diet and ammunition samples to determine the importance of ammunition as a source of exposure. Blood lead levels in pre-release condors were low (average 27.7 ng/mL, SD 4.9 ng/ mL) and isotopically similar to dietary and background environmental lead in California. In contrast, blood lead levels in free-flying condors were substantially higher (average 246 ng/mL, SD 229 ng/mL) with lead isotopic compositions that approached or matched those of the lead ammunition. A two-endmember mixing model defined by the background 207Pb/206Pb ratio of representative condor diet samples (0.8346) and the upper 207Pb/206Pb ratio of the ammunition samples (0.8184) was able to account for the blood lead isotopic compositions in 20 out of the 26 live condors sampled in this study (i.e., 77%). Finally, lead in tissues and in a serially sampled growing feather recovered postmortem from a lead-poisoned condor in Arizona evidence acute exposure from an isotopically distinct lead source. Together, these data indicate that incidental ingestion of ammunition in carcasses of animals killed by hunters is the principal source of elevated lead exposure that threatens the recovery in the wild of this endangered species.     

Behavioral science in the military: Research trends for the eighties.

Contends that several major activities related to combat readiness will engage military psychologists for at least the remainder of the decade. The organizational context of military psychology is described in terms of settings, development of the work program, and funding. The psychologist's role in dealing with problems of acquisition, retention, assignment, training of service members, human factors engineering, and organizational productivity is discussed. (1 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the error behavior in linear minimum variance estimation problems

For linear systems the error covariance matrix for the unbiased, minimum variance estimate of the state does not depend upon any specific realization of the measurement sequence. Thus it can be examined to determine the expected behavior of the error in the estimate before actually using the filter in practice. In this paper, the general linear system that contains both plant and measurement noise is shown to exhibit a decomposition property that permits the derivation of upper and lower bounds upon the error covariance matrix. This decomposition allows systems containing either plant or measurement noise, but not both, to be considered separately. Some general characteristics of these simpler systems are discussed and conditions for the positive definiteness and vanishing of the error covariance matrix are established. It is seen that the presence of plant noise, in general, prevents the error from vanishing. Alternatively, the condition ofq-stage observability is seen to be sufficient to insure that the error covariance matrix asymptotically approaches the zero matrix for systems with noise-free plants. These results are used to establish very specific lower bounds. Through the application of the duality principle, they can be applied directly to the analysis of the linear regulator problem.     

Least-squares estimation: from Gauss to Kalman

This discussion is directed to least-squares estimation theory, from its inception by Gauss1 to its modern form, as developed by Kalman.2 To aid in furnishing the desired perspective, the contributions and insights provided by Gauss are described and related to developments that have appeared more recently (that is, in the 20th century). In the author's opinion, it is enlightening to consider just how far (or how little) we have advanced since the initial developments and to recognize the truth in the saying that we ``stand on the shoulders of giants.'     

A note on the "fakability" of the Minnesota Teacher Attitude Inventory.

To test whether prospective teachers can fake the MTAI, and whether signing his name influences his score, 406 prospective teachers were administered the MTAI, first under standard directions and then under directions to "fake." Directions to "fake" resulted in significantly higher (more "progressive") attitude scores; under standard directions the anonymous respondents had a lower mean score than the signers. The implications for use of the Inventory in counseling and in selection are mentioned. (PsycINFO Database Record (c) 2010 APA, all rights reserved)