Copyright (c) 2009 All rights reserved. http://works.bepress.com/jchicharo Recent documents in Professor Joe F. Chicharo en-us Sun, 11 Oct 2009 14:54:03 PDT 3600 http://works.bepress.com/jchicharo/51 http://works.bepress.com/jchicharo/51 Mon, 02 Feb 2009 14:31:24 PST This paper presents a novel method to estimate displacement of a moving object based on model calibration in a weak feedback laser diode self-mixing system. A hybrid genetic algorithm is employed to locate the global minimum for the cost function which is constructed as the discrepancy between theoretically calculated system output and the experimental data. In turn, displacement measurement is achieved by identifying the optimal parameters for the system model. The proposed method is tested by both simulation and experimental setup with measuring accuracy better than 25nm. L. Wei http://works.bepress.com/jchicharo/52 http://works.bepress.com/jchicharo/52 Mon, 02 Feb 2009 14:31:24 PST This paper presents a novel neural network signal interpolation technique in order to eliminate the noise and disturbance associated with the self-mixing signal observed from optical feedback self- mixing interferometry (OFSMI). The proposed technique aims to improve the accuracy for displacement and moving track measurement of a target. The performance of the proposed approach is evaluated by both simulation and experimentation, with simulation revealing a measuring accuracy of A/25 for weak feedback and J20 for moderate feed back. L. Wei http://works.bepress.com/jchicharo/50 http://works.bepress.com/jchicharo/50 Mon, 02 Jun 2008 22:51:35 PDT We present a theoretical analysis on the locations of transition points in moderate feedback self-mixing signal which is a fundamental issue to be addressed in preprocessing experimentally acquired data. Locations for the start and end points for upward and downward switchings are calculated based on the Lang-Kobayashi model and discussions are given, which provides guidance in achieving more accurate signal normalization. L. Wei http://works.bepress.com/jchicharo/49 http://works.bepress.com/jchicharo/49 Mon, 02 Jun 2008 22:51:29 PDT The performance of structured light profilometers is significantly hindered by the generation of distorted sinusoid fringe images, particularly, for multi-channel applications. In this paper we investigate the application of neural network fringe calibration for the multi-channel approach. We analytically review the nature of the major error sources associated with the multi-channel approach and propose afringe calibration technique with emphasis on minimal photometric calibration. The performance of the calibration technique is gauged through both simulation and experimentation. M. Baker http://works.bepress.com/jchicharo/48 http://works.bepress.com/jchicharo/48 Mon, 02 Jun 2008 22:51:23 PDT This paper considers the issue of noise reduction associated with Optical Feedback Self-mixing Interferometries (OFSMI). The objective is to develop an effective pre-processing filtering solution that can eliminated the inherent noise disturbances. The characteristics of OFSMI signals are described in some detail and two filter solutions are proposed. The latter includes a non-linear median filter and a Kaiser based FIR filter. The performance of the two types of filters are removing sparkle-like noise while Kaiser based FIR filters areeffective in reducing the high frequency noise as well as the slow time-varying signal envelop fluctuation. Interestingly our results show that the best performance is achieved by combining the two filters, that is, a median filter followed by a Kaiser-based FIR filter. In other words, the estimation accuracy of OFSMI parameters such as the line-width enhancement factor (LEF) of semiconductor lasers is significantly improved with the aid of the proposed pre-processing solution. Y. Yu http://works.bepress.com/jchicharo/47 http://works.bepress.com/jchicharo/47 Wed, 28 May 2008 15:32:47 PDT Whilst linear prediction is the cornerstone of most modern speech coders, few of these coders incorporate the perceptual characteristics of hearing into the calculation of the linear predictor coefficients (LPCs). This paper proposes a method of incorporating simultaneous masking into the calculation of the LPCs. This modification requires only a modest increase in computational complexity and results in the linear predictor removing more perceptually important information from the input speech signal. This results in a filter that better models the formants of the input speech spectrum. The net effect is that an improvement in quality is achieved for a given bit rate or alternately a bit rate reduction can be achieved while maintaining perceived quality. These results have been confirmed through subjective listening tests. J. Lukasiak http://works.bepress.com/jchicharo/46 http://works.bepress.com/jchicharo/46 Wed, 28 May 2008 15:32:44 PDT We have proposed and demonstrated a new fiber Bragg grating (FBG) based vibration measurement system which can demodulate vibration signals from wavelength-multiplexed FBG sensors with high sensitivity and fast frequency response. E. Li http://works.bepress.com/jchicharo/45 http://works.bepress.com/jchicharo/45 Wed, 28 May 2008 15:32:40 PDT In this paper, a generalized analysis model for fringe pattern profilometry is presented. The new analysis model is derived mathematically, which describes the essential relationships between projected and deformed fringe patterns. With generalized analysis model, the projected fringe patterns used for profilometry can be arbitrary rather than being limited to be sinusoidal as those for the conventional approaches. Meanwhile, based on the proposed generalized model, a new algorithm is presented to reconstruct three-dimensional surfaces. Computer simulation results show that compared with the conventional model for fringe pattern profilometry, the generalized model and the proposed algorithm can significantly improve the three-dimensional reconstruction accuracy, especially when the projected fringe pattern is distorted by some unknown factors. Y. Hu http://works.bepress.com/jchicharo/44 http://works.bepress.com/jchicharo/44 Wed, 28 May 2008 15:32:37 PDT Integrated services IP networks are expected to provide a variety of services with differentiated QoS. This requires the implementation of mechanisms that can discriminate service classes in terms of QoS. The IETF has recently proposed a differentiated services (Diffserv) framework for provision of QoS. In this paper we analyse the performance of two Diffserv mechanisms: threshold dropping and priority scheduling in terms of packet loss and mean packet delay. A comparison of the two mechanisms is carried out with the requirement that both mechanisms provide the same level of packet loss for the preferred flow. This comparison extends the results reported in the literature for these two mechanisms. In particular, in this paper we determine the impact of buffer threshold and buffer size on packet loss and mean packet delay in these mechanisms. D. Jia http://works.bepress.com/jchicharo/43 http://works.bepress.com/jchicharo/43 Wed, 28 May 2008 15:32:34 PDT This paper presents a set of second-order recursive equations which are referred to as the second-order shift (SOS) properties of the discrete cosine transform (DCT) and the discrete sine transform (DST). The proposed SOS properties enable independent updating of the respective DCT and DST coefficients. This is in direct contrast with existing methodology for computing the running DCT and DST where there is an inherent interdependency between the DCT and DST coefficients. The SOS properties provide more efficient algorithms in terms of computational burden and memory requirements when implementing running DCTs and DSTs. J. Xi