Virtual Structures Based Autonomous Formation Flying Control for Small Satellites

Many space organizations have a growing need to fly several small satellites close together in order to collect and correlate data from different satellite sensors. To do this requires teams of engineers monitoring the satellites orbits and planning maneuvers for the satellites every time the satellite leaves its desired trajectory or formation. This task of maintaining the satellites orbits quickly becomes an arduous and expensive feat for satellite operations centers. This research develops and analyzes algorithms that allow satellites to autonomously control their orbit and formation without human intervention. This goal is accomplished by developing and evaluating a decentralized, optimization-based control that can be used for autonomous formation flight of small satellites. To do this, virtual structures, model predictive control, and switching surfaces are used. An optimized guidance trajectory is also develop to reduce fuel usage of the system. The Hill-Clohessy-Wiltshire equations and the D\u27Amico relative orbital elements are used to describe the relative motion of the satellites. And a performance comparison of the L1, L2, and L∞ norms is completed as part of this work. The virtual structure, MPC based framework combined with the switching surfaces enables a scalable method that allows satellites to maneuver safely within their formation, while also minimizing fuel usage

An Experiment Using Time-Based Detection in Flow Injection Analysis

We present a laboratory experiment, suitable for implementation in analytical chemistry courses at the undergraduate level, that demonstrates the utility of time-based measurements with doublet peaks in flow injection analysis. The measurements are taken with an instrument that incorporates a simple solid-state detector, which has as its source a light-emitting diode (LED) and as its detecting element a photodiode (PD). The system studied here is a simple acid-base titration. The experiment could be adapted to any number of chemical reactions that result in a product that absorbs light of the LED wavelength significantly

The LSST Data Mining Research Agenda

We describe features of the LSST science database that are amenable to scientific data mining, object classification, outlier identification, anomaly detection, image quality assurance, and survey science validation. The data mining research agenda includes: scalability (at petabytes scales) of existing machine learning and data mining algorithms; development of grid-enabled parallel data mining algorithms; designing a robust system for brokering classifications from the LSST event pipeline (which may produce 10,000 or more event alerts per night); multi-resolution methods for exploration of petascale databases; indexing of multi-attribute multi-dimensional astronomical databases (beyond spatial indexing) for rapid querying of petabyte databases; and more.Comment: 5 pages, Presented at the "Classification and Discovery in Large Astronomical Surveys" meeting, Ringberg Castle, 14-17 October, 200

Spin-Coupled Local Distortions in Multiferroic Hexagonal HoMnO3

Local structural measurements have been performed on hexagonal HoMnO3 in order to ascertain the specific changes in bond distances which accompany magnetic ordering transitions. The transition from paramagnetic to the antiferromagetic (noncollinear) phase near ~70 K is dominated by changes in the a-b plane Mn-Mn bond distances. The spin rotation transition near ~40 K involves both Mn-Mn and nearest neighbor Ho-Mn interactions while the low temperature transition below 10 K involves all interactions, Mn-Mn, Ho-Mn (nearest and next nearest) and Ho-Ho correlations. These changes in bond distances reveal strong spin-lattice coupling. The similarity in magnitude of the change in J(Mn-Mn) and J(Ho-Mn) enhances the system frustration. The structural changes are interpreted in terms of a model of competing spin order and local structural distortions. Density functional calculations are used to estimate the energies associated with ionic displacements. The calculations also reveal asymmetric polarization of the charge density of Ho, O3 and O4 sites along the z-axis in the ferroelectric phase. This polarization facilitates coupling between Ho atoms on neighboring planes normal to the z-axis.Comment: 8 figure

Archival researchers: An endangered species?

In recent years accounting historiography has been enriched by a considerable volume of debate surrounding the chronology and evolution of accounting theory and practice. By virtue of their attempts to explain the processes of change, accounting historians have become identified with a paradigm or world view that constitutes the theoretical context within which their research findings are couched. Scholars have either self-avowed their paradigmatic affiliations or have had their work so classified in the writings of others. Fleischman et al. [1996a], for example, trichotomized the field of industrial revolution cost accounting into three schools : the Neoclassical (economic rationalist), the Foucauldian, and the Marxist (labor process). A dichotomized schemata might be employed to distinguish critical and traditional historians. Critical historians tend to question the objectivity of much primary source material, particularly accounting documents, which can serve the self-interest of those in positions of power. Traditionalists have more faith that surviving business records provide a less partisan approximation of some sort of objective reality. A distinction can likewise be made between the new accounting history and older approaches, typically with a narrower focus. The new genre casts a wider net, deploying a variety of contexts to coexist with those economic aspects traditionally privileged in much accounting historiography. Many new accounting historians attempt to amplify the voices of suppressed groups (women, the poor, the illiterate) which have not been heard in mainstream literature

Accounting for interned Japanese-American civilians during World War II: Creating incentives and establishing controls for captive workers

On February 19, 1942, following the attack on Pearl Har­bor and the declaration of war against Japan, President Roosevelt is­sued Executive Order 9066 which empowered the Secretary of War to exclude any and all persons from designated areas in the United States. Shortly thereafter, some 120,000 civilians of Japanese descent were prohibited from living, working, or traveling on the West Coast. By October 1942, over 100,000 evacuees were relocated and con­fined to ten remote internment camps for the duration of the war. The War Relocation Authority (WRA) administered these camps and had the responsibility to feed, house, educate, and provide em­ployment for the evacuees. This article describes the WRA\u27s use of ac­counting information and situates the role of accounting within a la­bor-process framework. It initially discusses labor-process theory and provides an overview of the internment episode and cooperative ac­counting in the U.S. It then focuses on particular accounting policies, procedures, and reports that were used by the WRA to manage en­terprises, monitor internment activities, and socialize evacuees with American capitalistic values