100 research outputs found

    Exploiting Nonlinear Recurrence and Fractal Scaling Properties for Voice Disorder Detection

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    Background: Voice disorders affect patients profoundly, and acoustic tools can potentially measure voice function objectively. Disordered sustained vowels exhibit wide-ranging phenomena, from nearly periodic to highly complex, aperiodic vibrations, and increased "breathiness". Modelling and surrogate data studies have shown significant nonlinear and non-Gaussian random properties in these sounds. Nonetheless, existing tools are limited to analysing voices displaying near periodicity, and do not account for this inherent biophysical nonlinearity and non-Gaussian randomness, often using linear signal processing methods insensitive to these properties. They do not directly measure the two main biophysical symptoms of disorder: complex nonlinear aperiodicity, and turbulent, aeroacoustic, non-Gaussian randomness. Often these tools cannot be applied to more severe disordered voices, limiting their clinical usefulness.

Methods: This paper introduces two new tools to speech analysis: recurrence and fractal scaling, which overcome the range limitations of existing tools by addressing directly these two symptoms of disorder, together reproducing a "hoarseness" diagram. A simple bootstrapped classifier then uses these two features to distinguish normal from disordered voices.

Results: On a large database of subjects with a wide variety of voice disorders, these new techniques can distinguish normal from disordered cases, using quadratic discriminant analysis, to overall correct classification performance of 91.8% plus or minus 2.0%. The true positive classification performance is 95.4% plus or minus 3.2%, and the true negative performance is 91.5% plus or minus 2.3% (95% confidence). This is shown to outperform all combinations of the most popular classical tools.

Conclusions: Given the very large number of arbitrary parameters and computational complexity of existing techniques, these new techniques are far simpler and yet achieve clinically useful classification performance using only a basic classification technique. They do so by exploiting the inherent nonlinearity and turbulent randomness in disordered voice signals. They are widely applicable to the whole range of disordered voice phenomena by design. These new measures could therefore be used for a variety of practical clinical purposes.

    P4_7 Make a Brake for It!

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    AbstractThe paper investigates the plausibility of using a solar sail to reduce the orbital radius of a satellite around Mars instead of rocket thrusters. This is done by calculating the surface area of sail needed to lower the orbital radius from 3657km to 3517km by deploying the sail for a quarter of the orbit. The resulting surface area is 2.5x10 km2, which is impractical as a replacement for current methods

    P4_3 Total Free Fall

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    This paper analyses the logistics of The Fall, a fictional elevator through the Earth in the 2012 film Total Recall. In the film, it is claimed that the elevator can make its journey in 17 minutes by free falling through the centre of the planet. By modelling the actual free fall of an object in a vacuum through the Earth, it is shown that this trip would in fact take over 42 minutes. Drag forces were then considered, showing that without an external force The Fall would enter damped harmonic motion and would never reach its destination

    P4_2 Beam Me Up

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    The effects of sending a laser powered platform to low Earth orbit are investigated. We consider the effects of drag, attenuation by the atmosphere and divergence of the laser beam. It is found that a 1000kg platform could be accelerated to an altitude of 200km using an average laser power of 1.8 terawatts; however it is unfeasible to extend this argument to a much more massive space shuttle sized object

    P4_6 A Good Hose Down

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    This paper investigates the maximum pressure of a fire hydrant that a human can withstand before losing control due to the impulse at the hose aperture. The effects of static friction and the maximum grip force are compared, and it is found that at a hydrant pressure of 131KPa, a human will lose grip of the hose, whereas a pressure of 140KPa is required to cause the handler of the hose to begin to slide backwards

    Dealing with the Effect of Path Curvature on Consistency of Dead Reckoned Paths in Networked Virtual Environments

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    Several techniques exist which reduce network bandwidth consumption and thus limit the effects of network latency in networked virtual environments. Dead reckoning is one such technique that has been widely adopted for use with dynamic entities. However, in previous work we have shown that the use of a spatial threshold alone in dead reckoning can result in unbounded absolute inconsistency. A novel hybrid threshold was proposed that combined a spatial threshold together with an absolute consistency metric to impose an upper bound on absolute inconsistency under all circumstances. This was verified through a simulation of typical movement in a computer racing game. This paper extends this work by investigating the problem in more detail and verifying the hybrid threshold solution in live trials across the Internet. In particular the relationship between curvature of movement and absolute consistency is explored. The experimental trials allow a comparative analysis of how users behave when different threshold types are used under varying degrees of curvature. This work provides further justification for the use of a hybrid threshold approach when dead reckoning is employed in networked virtual environments