Vision-based obstacle detection for rotorcraft flight

The ability of rotorcraft to fly at low altitude is hindered by the high pilot workload required to avoid obstacles. The development of automation tools that can detect obstacles in the rotorcraft flight path, warn the crew, and interact with the guidance system to avoid detected obstacles would significantly reduce pilot workload and increase safety. This article describes an obstacle detection approach based on feature tracking and recursive range estimation that takes into account the characteristics of rotorcraft flight. The merits and weaknesses of the approach are discussed using image sequences from the laboratory and from flight. © 1992 John Wiley & Sons, Inc.     

Scattering of plane SH-waves by a cylindrical canyon of arbitrary shape in anisotropic media

The scattering and diffraction of plane SH-waves, by an arbitrary-shaped cylindrical canyon in anisotropic media is formulated here. Analytical solutions are obtained via the complex function theory, using the orthogonal property of the Hermite functions to solve the resulting set of infinite algebraic equations. Expressions for scattered displacements and scattered stresses are given. Three cross-sectional profile types are used in the numerical simulation of the two-dimensional canyon topography: (a) a semi-circular profile, (b) a semi-elliptical profile and (c) a triangular profile. The results obtained in (a) and (b) are consistent with known solutions computed by Trifunac and his co-workers [1,3] using a different method. As the exact solution for (c) is not known to exist, the result given here is believed to be new and would therefore serve as a useful check for numerical analysts working in this area.     

Some aspects of deformation behavior

The deformation behavior of several single- and two-phase coarse microstructures has been examined using microhardness measurements. It has been found that the strength response of a coarse phase in isolation is distinctly different from its response when it exists in a two-phase system. The second phase alters the mechanical state of the first one andvice versa even in the plastically undeformed condition. This phenomenon is explained in terms of the existence of an appreciable amount of residual stresses in two-phase coarse microstructures. These stresses primarily arise due to the difference in thermal expansion coefficients of the phases. The in- fluence of elastic stress field on microhardness response is shown with a new type of experiment to support the proposed explanation. The present results question the existing expressions for deformation modeling of multiphase materials because of the uncertainties in the estimation of the average strength of the phases in a two-phase system.     

A comparison of lightness contrast effects in CRT and surface colours

The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074     

Nicotine-stimulated release of [3H]norepinephrine from fetal rat locus coeruleus cells in culture

Acute nicotine administration stimulated [3H]norepinephrine ([3H]NE) release from cultured fetal locus coeruleus (LC) cells. The effect was concentration dependent, with an EC50 of 0.9 microM, and was abolished by removal of calcium from, or addition of tetrodotoxin (500 nM) to, the assay buffer. Other nicotinic receptor agonists stimulated [3H]NE release, with the rank order of potency being (+)-epibatidine > (-)-nicotine > 1,1-dimethyl-4-phenylpiperazinium (DMPP). Whereas (-)-nicotine and (+/-)-epibatidine exhibited equal maximal responses, DMPP was a partial agonist and (-)-cytisine had no agonist activity. Nicotine-stimulated release of [3H]NE was blocked by nicotinic receptor antagonists, with an order of potency of mecamylamine > lobeline > cytisine > methyllycaconitine > dihydro-beta-erythroidine. The pharmacological profile of this nicotinic receptor is largely consistent with that described previously for an alpha4beta2 subunit combination, although discrepancies in the efficacies of agonists were observed. No additivity in NMDA- and nicotine-stimulated [3H]NE release was observed, suggesting a common signal transduction mechanism. However, the pharmacological characteristics of MK-801 blockade of nicotine-induced responses were not consistent with those of an NMDA receptor. We therefore conclude that nicotine directly releases [3H]NE from LC cells and does not act indirectly via activation of glutamate release.     

Honey revisited: a reappraisal of honey in pre-industrial diets

In pre-industrial times, honey was the main source of concentrated sweetness in the diets of many peoples. There are no precise figures for per capita consumption during most periods in history because honey was part of either a hunter-gatherer or subsistence economy. Until now, historians and food writers have proposed that it was a scarce commodity available only to a wealthy few. We do know, however, that in a cash economy honey was sold in large units (gallons and even barrels) and it was present in such abundance that mead, made from honey, was a common alcoholic drink. A reappraisal of the evidence from the Stone Age, Antiquity, the Middle Ages and early Modern times suggests that ordinary people ate much larger quantities of honey than has previously been acknowledged. Intakes at various times during history may well have rivalled our current consumption of refined sugar. There are implications therefore for the role of sugar in modern diets. Refined sugar may not have displaced more nutrient-rich items from our present-day diets but only the nutritionally comparable food, honey.