Showing papers by "Albion College published in 1997"

Cooperative multi-robot observation of multiple moving targets

Abstract: An important issue that arises in the automation of many security, surveillance, and reconnaissance tasks is that of monitoring, or observing, the movements of targets navigating in a bounded area of interest. A key research issue in these problems is that of sensor placement-determining where sensors should be located to maintain the targets in view. In complex applications of this type, the use of multiple sensors dynamically moving over time is required. In this paper, we investigate the use of a cooperative team of autonomous sensor-based robots for multi-robot observation of multiple moving targets. We focus primarily on developing the distributed control strategies that allow the robot team to attempt to maximize the collective time during which each object is being observed by at least one robot in the area of interest. Our initial efforts in this problem address the aspects of distributed control in homogeneous robot teams with equivalent sensing and movement capabilities working in an uncluttered, bounded area. This paper first formalizes the problem, discusses related work, and then shows that this problem is NP-hard. We then present a distributed approximate approach to solving this problem that combines low-level multi-robot control with higher-level control. The low-level control is described in terms of force fields emanating from the targets and the robots. The higher level control is presented in the ALLIANCE formalism, which provides mechanisms for fault tolerant cooperative control, and allows robot team members to adjust their low-level actions based upon the actions of their teammates. We then present the results of the implementation of portions of our approach, both in simulation and on physical robots.

High-accuracy determination of the relative full energy peak efficiency curve of a coaxial HPGe detector in the energy range 700-1300 keV

Abstract: A method for the high-accuracy determination of the relative full energy peak efficiency is established. Radionuclides that emit at least two gamma-ray lines for which the relative intensity can be found (from the decay scheme) to much better than ±0.1% were used as calibration standards. Specifically, the 889 and 1120 keV lines of 46Sc, the 983 and 1312 keV lines of 48Sc, the 1173 and 1332 keV lines of 60Co, and the 702 and 871 keV lines of 94Nb were implemented. The high-accuracy calibration was taken to extend from the lowest line of 94Nb at 702 keV to the highest line of 60Co at 1332 keV. An analytical expression, based on linear least-squares fitting, was developed to describe the behavior of the relative efficiency curve in that energy range. As a result, the ability of predicting relative full energy peak efficiencies to within ±0.1% (over most of the energy range) was demonstrated. The presented method is applicable in any measurement that requires the minimum calibration bias in the determination of reaction rate ratios. Applications in Neutron Activation Analysis (NAA) and in nuclear reactor dosimetry represent examples of such situations.

Effect of egg covering and habitat on nest destruction by house wrens

Abstract: Birds nesting near House Wrens (Troglodytes aedon) risk having their eggs, nestlings, and nests destroyed. Damage by wrens may be reduced in Black-capped Chickadees (Parus atricapillus), Tufted Titmice (P. bicolor), and other parids by concealing eggs under nest material during the laying period, and in sympatric cavity-nesting species by nesting in different habitats from wrens. To test if eggs were protected by covering, prelaying wrens were challenged for 1 day with a set of two boxes placed 1 m from their nest, one with two artificial eggs (miniature marshmallows) lightly covered under fur, the other with two artificial eggs in an open cup. Results varied with stage of nest-building; in 41 trials where both exposed eggs were removed, covered eggs remained in only 4 of 15 (27%) trials near early nests containing few sticks, but in 17 of 26 (65%) trials near more advanced nests. To assess effects of nest site, a box with a cup nest was placed in each of three habitats 10 or 20 m from 29 wren nests. After 1 day of habituation, two artificial eggs were placed in each nest and left exposed for 1 day. Boxes in woodland interiors were less likely than boxes in fields and along edges to be visited by wrens at least once over 2 days (66 vs. 97% visited) and were less likely to have eggs removed (10 vs. 83% removed). Competitors for nesting cavities also may escape attacks by wrens through differences in breeding period, active defense of territories or nests, or renesting.

The Ministry of Amusements: Film, Commerce, and Politics in Germany, 1917–1945

Abstract: In the American edition of the memoirs of filmmaker Leni Riefenstahl there appears an excruciatingly funny error in terminology whereby Albert Speer, newly appointed as Hitler's armaments minister, is referred to as the \"Minister of Amusements.\" What makes this faux pas doubly hilarious is that it represents an indirect—and presumably unintentional—parody of Riefenstahl's extended claim in the book for the political innocence of her cinematic activities in the Third Reich. By the same token, however, this error is also central to a discussion of the books under review. Both Klaus Kreimeier and Eric Rentschler deal, in different ways, with the political and commercial uses of film as popular amusement. For these authors, there are no easy historical distinctions among the phenomena of film as entertainment, film as art, film as business, film as politics. Both books illuminate the dynamic social contexts in which films are made, distributed, shown, and viewed. Rentschler also offers fresh material and analysis for the recent historical excavation of the social history of the Third Reich and the hotly debated issues of \"resistance\" and \"collaboration\" under Hitler. Kreimeier, for his part, argues that during the classic era of German film in the 1920s \"Ufa's melodramas, comedies, Prussian films, waltz dreams,

Telling Tales in School

Abstract: Knowing our students, and our institutions, through their stories

Julio Cortázar's Axolotl: Literary Archaeology of the Unreal

Abstract: Axolotl (Final del juego, "end of the game"), one of Julio Cortazar's masterpieces, chronicles one man's discovery of the axolotls, rather unusuallooking amphibians, his growing obsession with them and, ultimately, his supposed transformation into an axolotl One of the better known and most frequently analyzed of all Cortazar's stories, Axolotl quickly establishes and perpetuates an aura of ambiguity surrounding the narrator and the axolotls which causes the reader to question the nature of reality 1 Consequently, the text's openness has fueled interpretive speculation with regard to a wide variety of topics, ranging from religion and Aztec mythology to philosophy and psychology Some readers view Axolotl as a commentary on the creative process itself, among them Alfred MacAdam, who writes that: "The philosophical problem of interpretation seems reduced in importance, displaced by the purely aesthetic problem of the representation of the unreal " Mac Adam's comment prompts the important question: How does Cortazar evoke a "representation of the unreal" that allows for such interpretive breadth? This study will consider how narrative strategies suggest that Cortazar's depiction of the "unreal" is inspired by a variety of literary sources, both classical and modern Cortazar draws from these other texts to infuse his own story with subtle, yet highly significant nuances A close reading will explore these fictional interrelationships and explain why Cortazar's vision of reality seems so multifaceted The examination of how Cortazar manipulates these allusions will lead to an even deeper appreciation for this magnificent tale