Analog implementations of auditory models

The challenge of making cost-effective implementations of auditory models has led us to pursue an analog VLSI micro-power approach. Experiments with the first few generations of analog cochlea chips showed some of both the potential and the problems of this approach. The inherent exponential behavior of MOS transistors in the subthreshold or weak-inversion region leads to nonlinear filter circuits, in which the small-signal and large-signal behaviors can be quite different. Early problems with instability, poor dynamic range, and excessive noise are now understood in terms of the transition behavior between these regions, and this understanding has led us to design filter stages with appropriately compressive behavior, resulting in more robust cochea performance. Several types of correlator circuits to follow the cochlea have also been developed into working demonstrations. Videotapes of circuit outputs and simulations illustrate the recent ideas and progress

Improved implementation of the silicon cochlea

The original “analog electronic cochlea” of Lyon and Mead (1988) used a cascade of second-order filter sections in subthreshold analog VLSI to implement a low-power, real-time model of early auditory processing. Experience with many silicon-cochlea chips has allowed the identification of a number of important design issues, namely dynamic range, stability, device mismatch, and compactness. In this paper, the original design is discussed in light of these issues, and circuit and layout techniques are described which significantly improve its performance, robustness, and efficiency. Measurements from test chips verify the improved performance

A decimated electronic cochlea on a reconfigurable platform.

Wong Chun Kit.Thesis submitted in: October 2006.Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (leaves 73-76).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Background and Motivation --- p.1Chapter 1.2 --- Objectives --- p.4Chapter 1.3 --- Contributions --- p.4Chapter 1.4 --- Thesis Outline --- p.5Chapter 2 --- Digital Signal Processing --- p.6Chapter 2.1 --- Introduction --- p.6Chapter 2.2 --- Discrete-time Signals and Systems --- p.7Chapter 2.2.1 --- Discrete-time Signals --- p.7Chapter 2.2.2 --- Discrete-time Signal Processing Systems --- p.9Chapter 2.2.3 --- Linear Time-Invariant (LTI) Systems --- p.10Chapter 2.3 --- Finite Impulse Response (FIR) Filters --- p.13Chapter 2.3.1 --- Introduction --- p.13Chapter 2.3.2 --- Windowing FIR Filter Design Method --- p.15Chapter 2.4 --- Infinite Impulse Response (IIR) Filters --- p.17Chapter 2.4.1 --- Introduction --- p.17Chapter 2.4.2 --- Bilinear Transform IIR Filter Design Method --- p.18Chapter 2.4.3 --- Spectral Transformations of IIR Filters --- p.22Chapter 2.5 --- Comparison on FIR and IIR Filters --- p.25Chapter 2.6 --- Digital Signal Resampling --- p.26Chapter 2.6.1 --- Introduction --- p.26Chapter 2.6.2 --- Resampling by Decimation --- p.26Chapter 2.6.3 --- Resampling by Interpolation --- p.28Chapter 2.6.4 --- Resampling by a Rational Factor --- p.29Chapter 2.7 --- Introduction to Dual Fixed-point (DFX) Representation --- p.30Chapter 2.8 --- Summary --- p.33Chapter 3 --- Lyon and Mead's Cochlea Model --- p.34Chapter 3.1 --- Introduction --- p.34Chapter 3.2 --- Digital Cochlea Model: Cascaded IIR Filters --- p.37Chapter 3.2.1 --- Introduction --- p.37Chapter 3.2.2 --- Bandwidth and Centre frequencies --- p.38Chapter 3.2.3 --- Zeros and Poles --- p.39Chapter 3.3 --- Modifications for Decimated Cochlea Model --- p.41Chapter 3.3.1 --- Introduction --- p.41Chapter 3.3.2 --- Aliasing Avoidance --- p.42Chapter 3.3.3 --- Coefficient Modification after Decimation --- p.43Chapter 3.4 --- Summary --- p.47Chapter 4 --- System Architecture --- p.48Chapter 4.1 --- Introduction --- p.48Chapter 4.2 --- Hardware Platform and CAD Tools --- p.48Chapter 4.3 --- Sequential Processing Electronic Cochlea --- p.51Chapter 4.3.1 --- Pipelining - An Interleaving Scheme --- p.53Chapter 4.3.2 --- Decimation in Sequential Processing Electronic Cochlea . --- p.54Chapter 4.3.3 --- Multiple Sequential Cores --- p.55Chapter 4.3.4 --- Architecture of the DFX Filter Computation Core --- p.55Chapter 4.4 --- Summary --- p.60Chapter 5 --- Experimental Results --- p.61Chapter 5.1 --- Introduction --- p.61Chapter 5.2 --- Testing Environment --- p.61Chapter 5.3 --- Performance of the Sequential Electronic Cochlea --- p.63Chapter 5.3.1 --- Comparisons --- p.63Chapter 5.4 --- Summary --- p.69Chapter 6 --- Conclusions --- p.70Chapter 6.1 --- Future Work --- p.72Bibliography --- p.7

Biomimetic Based Applications

The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions