Location of planar targets in three space from monocular images

Many pieces of existing and proposed space hardware that would be targets of interest for a telerobot can be represented as planar or near-planar surfaces. Examples include the biostack modules on the Long Duration Exposure Facility, the panels on Solar Max, large diameter struts, and refueling receptacles. Robust and temporally efficient methods for locating such objects with sufficient accuracy are therefore worth developing. Two techniques that derive the orientation and location of an object from its monocular image are discussed and the results of experiments performed to determine translational and rotational accuracy are presented. Both the quadrangle projection and elastic matching techniques extract three-space information using a minimum of four identifiable target points and the principles of the perspective transformation. The selected points must describe a convex polygon whose geometric characteristics are prespecified in a data base. The rotational and translational accuracy of both techniques was tested at various ranges. This experiment is representative of the sensing requirements involved in a typical telerobot target acquisition task. Both techniques determined target location to an accuracy sufficient for consistent and efficient acquisition by the telerobot

Magnetic-induced phonon anisotropy in ZnCr2_2O4_4 from first principles

We have studied the influence of magnetic order on the optical phonons of the geometrically frustrated spinel ZnCr$_2$O$_4$ from first-principles. By mapping the first-principles phonon calculations onto a Heisenberg-like model, we developed a method to calculate exchange derivatives and subsequently the spin-phonon couping parameter from first-principles. All calculations were performed within LSDA+U

Half-Heusler semiconductors as piezoelectrics

One of the central challenges in materials science is the design of functional and multifunctional materials, in which large responses are produced by applied fields and stresses. A rapidly developing paradigm for the rational design of such materials is based on the first-principles study of a large materials family, the perovskite oxides being the prototypical case. Specifically, first-principles calculations of structure and properties are used to explore the microscopic origins of the functional properties of interest and to search a large space of equilibrium and metastable phases to identify promising candidate systems. In this paper, we use a first-principles rational-design approach to demonstrate semiconducting half-Heusler compounds as a previously-unrecognized class of piezoelectric materials, and to provide guidance for the experimental realization and further investigation of high-performance materials suitable for practical applications.Comment: 5 pages, 3 figues, 3 table

Breeding for improved responsiveness to arbuscular mycorrhizal fungi in onion

Arbuscular mycorrhizal fungi (AMF) play an important role in the uptake of nutrients and water from soil. Onions, Allium cepa L., are plants with a shallow root system. As a result, onion plants need a lot of fertiziler for their growth. Furthermore, onion plants are sensitive to drought. The aim of the current research project is to study the beneficial effect of mycorrhizal fungi on the growth and development of Allium species and to determine whether it is possible to improve onions for mycorrhizal responsiveness by means of breeding. Variation among Allium species and segregation observed in a interspecific tri-hybrid population indicate that selection and thus breeding for high responsiveness to AMF is possible