Internal representations of temporal statistics and feedback calibrate motor-sensory interval timing.

Humans have been shown to adapt to the temporal statistics of timing tasks so as to optimize the accuracy of their responses, in agreement with the predictions of Bayesian integration. This suggests that they build an internal representation of both the experimentally imposed distribution of time intervals (the prior) and of the error (the loss function). The responses of a Bayesian ideal observer depend crucially on these internal representations, which have only been previously studied for simple distributions. To study the nature of these representations we asked subjects to reproduce time intervals drawn from underlying temporal distributions of varying complexity, from uniform to highly skewed or bimodal while also varying the error mapping that determined the performance feedback. Interval reproduction times were affected by both the distribution and feedback, in good agreement with a performance-optimizing Bayesian observer and actor model. Bayesian model comparison highlighted that subjects were integrating the provided feedback and represented the experimental distribution with a smoothed approximation. A nonparametric reconstruction of the subjective priors from the data shows that they are generally in agreement with the true distributions up to third-order moments, but with systematically heavier tails. In particular, higher-order statistical features (kurtosis, multimodality) seem much harder to acquire. Our findings suggest that humans have only minor constraints on learning lower-order statistical properties of unimodal (including peaked and skewed) distributions of time intervals under the guidance of corrective feedback, and that their behavior is well explained by Bayesian decision theory.

Vowel normalisation: Time-domain processing of the internal dynamics of speech

Human listeners can identify vowels regardless of speaker size, although the sound waves for an adult and a child speaking the ’same’ vowel would differ enormously. The differences are mainly due to the differences in vocal tract length (VTL) and glottal pulse rate (GPR) which are both related to body size. Automatic speech recognition machines are notoriously bad at understanding children if they have been trained on the speech of an adult. In this paper, we propose that the auditory system adapts its analysis of speech sounds, dynamically and automatically to the GPR and VTL of the speaker on a syllable-to-syllable basis. We illustrate how this rapid adaptation might be performed with the aid of a computational version of the auditory image model, and we propose that an auditory preprocessor of this form would improve the robustness of speech recognisers.

Turbulence length scale measurements in a motored internal combustion engine

A novel technique, using a 'flying' Hot Wire Anemometer is described; it is shown how the turbulent structure in a motored engine, using a high molecular weight gas as the working fluid, may be investigated with relative simplicity and very little engine modification. Initial results are presented for integral and micro length scales, which are within the range expected based on previous work. Copyright © 1987 Society of Automotive Engineers, Inc.

Large eddy simulation of turbine internal cooling ducts

Abstract Large-Eddy Simulation (LES) and hybrid Reynolds-averaged Navier–Stokes–LES (RANS–LES) methods are applied to a turbine blade ribbed internal duct with a 180° bend containing 24 pairs of ribs. Flow and heat transfer predictions are compared with experimental data and found to be in agreement. The choice of LES model is found to be of minor importance as the flow is dominated by large geometric scale structures. This is in contrast to several linear and nonlinear RANS models, which display turbulence model sensitivity. For LES, the influence of inlet turbulence is also tested and has a minor impact due to the strong turbulence generated by the ribs. Large scale turbulent motions destroy any classical boundary layer reducing near wall grid requirements. The wake-type flow structure makes this and similar flows nearly Reynolds number independent, allowing a range of flows to be studied at similar cost. Hence LES is a relatively cheap method for obtaining accurate heat transfer predictions in these types of flows.

Mixing and internal dynamics of droplets impacting and coalescing on a solid surface.

The coalescence and mixing of a sessile and an impacting liquid droplet on a solid surface are studied experimentally and numerically in terms of lateral separation and droplet speed. Two droplet generators are used to produce differently colored droplets. Two high-speed imaging systems are used to investigate the impact and coalescence of the droplets in color from a side view with a simultaneous gray-scale view from below. Millimeter-sized droplets were used with dynamical conditions, based on the Reynolds and Weber numbers, relevant to microfluidics and commercial inkjet printing. Experimental measurements of advancing and receding static contact angles are used to calibrate a contact angle hysteresis model within a lattice Boltzmann framework, which is shown to capture the observed dynamics qualitatively and the final droplet configuration quantitatively. Our results show that no detectable mixing occurs during impact and coalescence of similar-sized droplets, but when the sessile droplet is sufficiently larger than the impacting droplet vortex ring generation can be observed. Finally we show how a gradient of wettability on the substrate can potentially enhance mixing.

Locally oxidized silicon surface-plasmon Schottky detector for telecom regime.

We experimentally demonstrate an on-chip nanoscale silicon surface-plasmon Schottky photodetector based on internal photoemission process and operating at telecom wavelengths. The device is fabricated using a self-aligned approach of local-oxidation of silicon (LOCOS) on silicon on insulator substrate, which provides compatibility with standard complementary metal-oxide semiconductor technology and enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. Additionally, LOCOS technique allows avoiding lateral misalignment between the silicon surface and the metal layer to form a nanoscale Schottky contact. The fabricated devices showed enhanced detection capability for shorter wavelengths that is attributed to increased probability of the internal photoemission process. We found the responsivity of the nanodetector to be 0.25 and 13.3 mA/W for incident optical wavelengths of 1.55 and 1.31 μm, respectively. The presented device can be integrated with other nanophotonic and nanoplasmonic structures for the realization of monolithic opto-electronic circuitry on-chip.

Locally oxidized silicon surface-plasmon Schottky detector for telecom regime

We experimentally demonstrate an on-chip nanoscale silicon surface-plasmon Schottky photodetector based on internal photoemission process and operating at telecom wavelengths. The device is fabricated using a self-aligned approach of local-oxidation of silicon (LOCOS) on silicon on insulator substrate, which provides compatibility with standard complementary metal-oxide semiconductor technology and enables the realization of the photodetector and low-loss bus photonic waveguide at the same fabrication step. Additionally, LOCOS technique allows avoiding lateral misalignment between the silicon surface and the metal layer to form a nanoscale Schottky contact. The fabricated devices showed enhanced detection capability for shorter wavelengths that is attributed to increased probability of the internal photoemission process. We found the responsivity of the nanodetector to be 0.25 and 13.3 mA/W for incident optical wavelengths of 1.55 and 1.31 μm, respectively. The presented device can be integrated with other nanophotonic and nanoplasmonic structures for the realization of monolithic opto-electronic circuitry on-chip. © 2011 American Chemical Society.