Browsing by Author "Lo, PC"

Now showing 1 - 17 of 17

A novel algorithm for computing the 2D split-vector-radix FFT
(2004-03-01)
Huang, HY
;
Lee, YY
;
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a novel two-dimensional split-vector-radix fast-Fourier-transform (2D svr-FFT) algorithm. The modularizing feature of the 2D svr-FFT structure enables us to explore its characteristics by identifying the local structural property. Each local module is designated as a DFT (non-DFT) block if its output corresponds to DFT (non-DFT) values. The block attribute (DFT or non-DFT) directs the algorithm to construct the local module. We will show that the distribution of DFT blocks can be illustrated by the Sierpinski triangle-a class of fractals generated by IFS (iterated function system). The finding of the Sierpinski-triangle structural property enables us to actually implement the 2D svr-FFT algorithm. To the best of our knowledge, the 2D svr-FFT has never been realized in software. The computational efficiency of the proposed algorithm is considerably improved in comparison with that provided by Matlab. (C) 2003 Elsevier B.V. All rights reserved.
Adaptive baseline correction of meditation EEG
(2001-06-01)
Lo, PC
;
Leu, JS
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In our study of EEG during Zen-Buddhism meditation, EEG signals recorded sometimes exhibit complex baseline drift caused by eye movement, deep breathing, etc. The baseline drift affects the grading of stages of meditation according to EEG rhythms. This paper describes a new method for EEG baseline drift correction. The method, utilizing the adaptive scheme, is able to extract the complex baseline drift pattern involving both slowly-varying and sharply-contoured transient activities. Compared with the conventional filtering approach, the proposed method proves its superiority in correcting the EEG contaminated by complex baseline drift patterns.
An approach to quantifying the multi-channel EEG spatial-temporal feature
(2000)
Lo, PC
;
Chung, WP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Investigation of spatial characteristics in the multi-channel EEG (electroencephalogram) has been of great importance to the fundamental and clinical medicine. Conventional methods are mostly based on the coherence and correlation analysis in time and frequency domain. The authors present the method of quantifying the global waveform complexity in EEG by analyzing the high-dimensional state-space trajectory constructed from the multi-channel EEG. The resulting average complexity index (<()over bar>) is well distinct between the background (4.0 similar to 4.5) and event (3.0 similar to 3.5 for the focal-sharp-wave transient) in the 5-channel case study. In addition, the running <()over bar> measurement for different electrode arrays, for a fixed number of state-space dimension (n = 5), reveals the EEG spatial characteristic. An array composed of nearby channels with similar EEG activities tends to have a small <()over bar>. On the other hand, the computed <()over bar> increases as the array consists of electrode sites with spatially incorrelated EEG activities. Thus the method is capable of quantifying the spatial-temporal feature of the multi-channel EEG.
An efficient FFT algorithm based on building on-line butterfly sub-structure
(1998)
Lee, YY
;
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a new method of implementing the fast Fourier transform (FFT), the "real-time FFT algorithm", which efficiently utilizes the computer time to perform the FFT computation while the data acquisition proceeds. The main idea is to build the local butterfly modules using the data points available. The algorithm is based on the decimation-in-time split-radix FFT (DIT sr-FFT) butterfly structure. The algorithm is superior to the conventional whole-block FET algorithm in synchronizing with the on-line process. The time delay is about 2/r that of the whole-block algorithm considering the FFT size N=2(r).
An efficient method for quantifying the multichannel EEG spatial-temporal complexity
(2001-03-01)
Lo, PC
;
Chung, WP
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The complexity index (delta) quantifies the intrinsic dimensionality of the global complexity of a point set, and was shown to be able to characterize electroencephalogram spatial-temporal features. The complexity index is conceptually comprehensible and easily implemented, yet, it is time consuming. In this paper, we present an efficient computational method based on the projection of the high-dimensional state-space points onto a one-dimensional axis. The computational time decreases by at least 50%, without affecting the measure accuracy.
An investigation of inner light during Zen meditation using alpha-suppressed EEG and VEP
(2005)
Chang, KM
;
Liu, CY
;
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Sensitivity to light is a common experience during prayer or Zen meditation, in both western and eastern cultures. Higher levels of happiness and lower health insurance costs are typical for those who experience inner tight. In this report, the connection between the experience of inner light and Zen meditation is investigated by using EEG and flash visual evoked potential (F-VEP) recorded from the occipital site Oz. EEG results indicate that the experience of inner light during Zen meditation by experienced practitioners is also accompanied by a large amount of alpha-suppressed EEG. The F-VEP data also reflect shorter latency, and indicates a stronger and more sensitive visual response during Zen meditation. These data are also the typical physiological responses when the eyes are open during a rested conscious state, and thus provide a possible closer connection between Zen meditation and the sensitivity of inner light.
Applicability of phase-locked loop to tracking the rhythmic activity in EEGS
(2000)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Conventional methods of spectral analysis are based on mathematical or numerical algorithms applied to digitized signals. This paper discusses the applicability of the phase-locked loop (PLL) approach for tracking electroencephalogram (EEG) rhythmic bands (delta, theta, alpha, or beta). The use of the PLL for frequency tracking should also aid the development of online EEG interpretation and screening based on frequency characteristics when the PLL is realized by hardware. As a result, two factors in the applicability of the PLL are: (1) translation of the EEG spectrum to a higher-frequency band by a single-sideband (SSB) modulation scheme, and (2) the narrowband spectral feature of the EEG-a small difference between two major frequencies. The PLL output is further quantized according to the EEG rhythmic bands. Our analysis shows that the integrated system is capable of tracking the EEG rhythmic patterns.
Categorization of EEG rhythmic patterns based on PLL approach
(2000)
Lee, YY
;
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper demonstrates a new approach based on phase-locked loop (PLL) model to categorizing the EEG (electroencephalogram) rhythmic band (delta, theta, alpha, or beta). The main idea is to translate the EEG spectrum to a higher frequency band by single-sideband (SSB) modulation scheme. A few factors determine the system performance in EEG analysis. According to the results of computer simulation, a satisfactory performance can be achieved by using the PLL model with a properly selected loop gain and loop-filter bandwidth.
EEG alpha blocking correlated with perception of inner light during Zen meditation
(2003)
Lo, PC
;
Huang, ML
;
Chang, KM
;
電控工程研究所
;
Institute of Electrical and Control Engineering
According to the experimental results and practitioners' subjective experience, we report some hypotheses that may account for meditative phenomena during the practice of Zen-Buddhism. Orthodox Zen-Buddhist practitioners, aiming to prove the most original true-self, discover and uncover the inner energy or light on the way towards their goal. Perception of the inner light can be comprehended as resonance. Uncovering the inner energy optimizes physiological and mental health. In the meditation experiment, a significant correlation was observed between perception of the inner light and electroencephalographic (EEG) alpha blockage. We further examined this phenomenon by recording the EEG from subjects during a blessing that the subjects did not know being given. During the blessing period, significant alpha blocking was observed in experimental subjects who had been practicing meditation for years in preparation for being in resonance with the inner light. This report provides a new insight into the debate that meditation benefits our health.
Quantification of the pseudo-periodicity in EEG
(2000-03-01)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Some EEG signals possess pseudo-periodicity, which is difficult to identify, and quantify. This paper points out the problems and proposes a straightforward approach for analyzing this long-term, extra low-rate rhythmicity (the fundamental frequency). The effect of pseudo periodicity on the Fourier spectrum is investigated. To process the enormous number of data points often encountered in this kind of signal, we adopt the down-sampling scheme in the field of multi-rate signal processing. In addition, waveform rectification is introduced to enhance the capability in detecting the number of pseudo periods. The experimental results demonstrate that the Fourier analysis, in combination with the down-sampling and amplitude-rectified processes, is feasible for quantifying the fundamental frequency and pseudo period of the EEG.
Real-time FFT algorithm applied to on-line spectral analysis
(1999-01-01)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
On-line running spectral analysis is of considerable interest in many electrophysiological signals, such as the EEG (electroencephalograph). This paper presents a new method of implementing the fast Fourier transform (FFT) algorithm. Our "real-time FFT algorithm" efficiently utilizes computer time to perform the FFT computation while data acquisition proceeds so that local butterfly modules are built using the data points that are already available. The real-time FFT algorithm is developed using the decimation-in-time split-radix FFT (DIT sr-FFT) butterfly structure. In order to demonstate the synchronization ability of the proposed algorithm, the authors develop a method of evaluating the number of arithmetic operations that it requires. Both the derivation and the experimental result show that the real-time FFT algorithm is superior to the conventional whole-block FFT algorithm in synchronizing with the data acquisition process. Given that the FFT size N = 2(r), real-time implementation of the FFT algorithm requires only 2/r the computational time required by the whole-block FFT algorithm.
Real-time FFT algorithm applied to on-line spectral analysis
(1999-01-01)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
On-line running spectral analysis is of considerable interest in many electrophysiological signals, such as the EEG (electroencephalograph). This paper presents a new method of implementing the fast Fourier transform (FFT) algorithm. Our "real-time FFT algorithm" efficiently utilizes computer time to perform the FFT computation while data acquisition proceeds so that local butterfly modules are built using the data points that are already available. The real-time FFT algorithm is developed using the decimation-in-time split-radix FFT (DIT sr-FFT) butterfly structure. In order to demonstate the synchronization ability of the proposed algorithm, the authors develop a method of evaluating the number of arithmetic operations that it requires. Both the derivation and the experimental result show that the real-time FFT algorithm is superior to the conventional whole-block FFT algorithm in synchronizing with the data acquisition process. Given that the FFT size N = 2(r), real-time implementation of the FFT algorithm requires only 2/r the computational time required by the whole-block FFT algorithm.
Real-time implementation of the moving FFT algorithm
(1999-12-01)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
An integrated algorithm for analyzing the real-time, running Fourier spectra is presented. When applying to the real-time analysis, the computational efficiency and synchronization ability are highly improved by integrating the recursive procedure with the real-time implementation strategy. Given the FFT (frame) size N = 2(r) and moving size M = 2(p), the algorithm implements the recursive procedure for updating the succeeding decomposed (into size N/M) DFTs at the (r - p)th stage, and thereafter constructs the sr-FFT (split-radix fast-Fourier-transform) butterfly modules in a real-time way. The recursive procedure highly reduces the number of complex arithmetic operations when the moving size M is small. The real-time implementation scheme enables the running spectral analysis to better synchronize with the data acquisition process. The computational complexity of the integrated algorithm is analyzed in detail, which shows the dependence of the number of complex arithmetic operations on the ratio N/M. The experimental result tested on Pentium 66 agrees with the analysis. (C) 1999 Elsevier Science B.V. All rights reserved.
Real-time implementation of the split-radix FFT - An algorithm to efficiently construct local butterfly modules
(1998-12-01)
Lo, PC
;
Lee, YY
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Spectral analysis of blood circulation based on the viewpoint of resonance
(2006-04-01)
Wei, CC
;
Lo, PC
;
Wu, LK
;
電控工程研究所
;
電信工程研究所
In this paper, we present a novel idea for analyzing blood circulation that is viewed as an electrical-driving, mechanical-pumping mechanism. Considering the electrocardiogram (ECG) and blood pressure wave (BPW) as the input and output signals of the system, we aim to quantify the spectral behavior of blood circulation from the viewpoint of resonance. First, the power spectrum of the ECG coincides well with that of the BPW for healthy subjects, but deviates significantly front the BPW's for vascular patients. Second, bispectral analysis demonstrates a strong phase coupling between ECG and BPW in healthy Subjects and a weaker coupling for subjects with vascular problems. Third, the transfer function for healthy subjects exhibits a flatter magnitude than that for patients. In addition, we propose a resonance circuit model of the spectral domain to represent blood circulation. The quality factor also exhibits better resonance characteristics for the healthy group than for the patient group.
System analysis of blood circulation based on coherence power transfer: From electrical driving to mechanical vibration
(2006-04-01)
Wei, CC
;
Lo, PC
;
Wu, LK
;
電控工程研究所
;
電信工程研究所
We analyze blood circulation based on the basis of the system viewpoint and coherence power transfer from electrical energy (ECG) to mechanical power (blood pressure wave). The coherent oscillation between the driving signal and the vibration of the cardiovascular system is investigated by coherence function and the perturbations of the system are found. In addition, we develop a mathematical equation to describe the phenomenon. The average peak coherence value S for the first live harmonics is utilized as an index to quantify the power coherence effect. The evaluated p-value (< 0.01) reveals that the distinction of power coherence between the healthy subjects and cardiovascular patients is significant. Consequently, we conclude that if the S approaches a value close to one, the output is almost completely attributed to input and fewer perturbation signals influence the system: therefore, the cardiovascular system stays in a better condition. Conversely, if S approaches a value less than one, larger perturbations will worsen the cardiovascular system condition.
Three-dimensional filtering approach to brain potential mapping
(1999-05-01)
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
The spatial distribution of electroencephalogram (EEG) features on the scalp surface, both in time or frequency, is of great importance in clinical applications and medical research. Traditionally, mathematical methods based on interpolation algorithms have been widely applied to obtain the EEG mappings, This paper presents an innovative approach to reconstructing the brain potential mappings from multichannel EEG's, The three-dimensional (3-D) filtering approach, differing from the numerical interpolating methods, considers the spatial distribution of brain potentials as a 3-D signal, which is processed and interpolated according to its spatial frequency characteristics, The performance of the 3-D filtering method evaluated on simulated brain potentials is shown to be comparable to the four-nearest-neighbors method. Moreover, the 3-D filtering method is superior to the spherical splines method in efficiency. Two main advantages of this method are: the prospect of developing realtime, animated EEG mappings utilizing powerful digital signal processors and its capability of processing and interpolating the brain potentials on the realistic irregular scalp surface.