Multiple object tracking with non-unique data-to-object association via generalized hypothesis testing

A generalized hypothesis testing approach is applied to the problem of tracking several objects where several different associations of data with objects are possible. Such problems occur, for instance, when attempting to distinctly track several aircraft maneuvering near each other or when tracking ships at sea. Conceptually, the problem is solved by first, associating data with objects in a statistically reasonable fashion and then, tracking with a bank of Kalman filters. The objects are assumed to have motion characterized by a fixed but unknown deterministic portion plus a random process portion modeled by a shaping filter. For example, the object might be assumed to have a mean straight line path about which it maneuvers in a random manner. Several hypothesized associations of data with objects are possible because of ambiguity as to which object the data comes from, false alarm/detection errors, and possible uncertainty in the number of objects being tracked. The statistical likelihood function is computed for each possible hypothesized association of data with objects. Then the generalized likelihood is computed by maximizing the likelihood over parameters that define the deterministic motion of the object

Spray coating apparatus having a rotatable workpiece holder

A spray coating apparatus is provided for rotating a workpiece relative to a spray station to obtain a uniform coating of the workpiece. In a typical example, the workpiece comprises a ceramic tile which is to be coated with a ceramic coating and the tile is to be used as a reusable component of the thermal protection system for a space shuttle. The apparatus for rotating the workpiece includes a base support having a first rotatable stage for rotation in the horizontal plane and a second rotatable stage for rotation in a second plane inclined at an angle, such as 45 degrees, to the horizontal plane and the workpiece is supported on this second stage. Thus the workpiece is rotatable in both of two planes of rotation

Causes of soil acidity

The introduction of agriculture into australia has caused many of our soils to become more acid faster than they would have otherwise. In Europe and other parts of the world, soil acidification is accepted as a normal by-product of a successful agricultural system. Lime* is widley used to neutralise the acids added as a result of agricultural practices. In Western Australia, lime applications will be needed more frequently in the future, although maybe not in the same volumes as in Europe

Practical applications of interactive voice technologies: Some accomplishments and prospects

A technology assessment of the application of computers and electronics to complex systems is presented. Three existing systems which utilize voice technology (speech recognition and speech generation) are described. Future directions in voice technology are also described

A Weakly Nonlinear Analysis of Impulsively-Forced Faraday Waves

Parametrically-excited surface waves, forced by a periodic sequence of delta-function impulses, are considered within the framework of the Zhang-Vi\~nals model (J. Fluid Mech. 1997). The exact impulsive-forcing results, in the linear and weakly nonlinear regimes, are compared with numerical results for sinusoidal and multifrequency forcing. We find surprisingly good agreement between impulsive forcing results and those obtained using a two-term truncated Fourier series representation of the impulsive forcing function. As noted previously by Bechhoefer and Johnson (Am. J. Phys. 1996), in the case of two equally-spaced impulses per period there are only subharmonic modes of instability. The familiar situation of alternating subharmonic and harmonic resonance tongues emerges for unequally-spaced impulses. We extend the linear analysis for two impulses per period to the weakly nonlinear regime for one-dimensional waves. Specifically, we derive an analytic expression for the cubic Landau coefficient in the bifurcation equation as a function of the dimensionless fluid parameters and spacing between the two impulses. As the capillary parameter is varied, one finds a parameter region of wave amplitude suppression, which is due to a familiar 1:2 spatio-temporal resonance between the subharmonic mode of instability and a damped harmonic mode. This resonance occurs for impulsive forcing even when harmonic resonance tongues are absent from the neutral stability curve. The strength of this resonance feature can be tuned by varying the spacing between the impulses. This finding is interpreted in terms of a recent symmetry-based analysis of multifrequency forced Faraday waves by Porter, Topaz and Silber (Phys. Rev. Lett. 2004, Phys. Rev. E 2004).Comment: 13 pages, 10 figures, submitted to Physical Review

Broken symmetries and pattern formation in two-frequency forced Faraday waves

We exploit the presence of approximate (broken) symmetries to obtain general scaling laws governing the process of pattern formation in weakly damped Faraday waves. Specifically, we consider a two-frequency forcing function and trace the effects of time translation, time reversal and Hamiltonian structure for three illustrative examples: hexagons, two-mode superlattices, and two-mode rhomboids. By means of explicit parameter symmetries, we show how the size of various three-wave resonant interactions depends on the frequency ratio m:n and on the relative temporal phase of the two driving terms. These symmetry-based predictions are verified for numerically calculated coefficients, and help explain the results of recent experiments.Comment: 4 pages, 6 figure

Barley production and soil acidity

One of the causes of reduced plant yields on acid soils is aluminium toxicity. because barley is extremely sensitive to this mineral, a project started last year to examine the influence of soil acidity on barley production in the main barley growing areas of Western Australia. This article discusses some of the background information on the project and its aims