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- Sheng Lu, He Zhao MS, +4 authors Ki H. Chon
- Journal of Clinical Monitoring and Computing
- 2007

Heart rate variability (HRV), extracted from an electrocardiogram, is known to be a noninvasive indicator reflecting the dynamic interplay between perturbations to cardiovascular function and the dynamic response of the cardiovascular regulatory system. Photoplethysmography (PPG) is a noninvasive method to monitor arterial oxygen saturation on a continuous… (More)

- Yuru Zhong, Hengliang Wang, Kihwan Ju, Kung-Ming Jan, Ki H. Chon
- IEEE Trans. Biomed. Engineering
- 2004

This paper introduces a modified principal dynamic modes (PDM) method, which is able to separate the dynamics of sympathetic and parasympathetic nervous activities. The PDM is based on the principle that among all possible choices of expansion bases, there are some that require the minimum number of basis functions to achieve a given mean-square… (More)

- Ki H. Chon, Shishir Dash, Kihwan Ju
- IEEE Trans. Biomed. Engineering
- 2009

We present a new method that uses the pulse oximeter signal to estimate the respiratory rate. The method uses a recently developed time-frequency spectral estimation method, variable-frequency complex demodulation (VFCDM), to identify frequency modulation (FM) of the photoplethysmogram waveform. This FM has a measurable periodicity, which provides an… (More)

- Hengliang Wang, Kin Siu, Kihwan Ju, Ki H. Chon
- Annals of Biomedical Engineering
- 2005

A high resolution approach to estimating time-frequency spectra (TFS) and associated amplitudes via the use of variable frequency complex demodulation (VFCDM) is presented. This is a two-step procedure in which the previously developed time-varying optimal parameter search (TVOPS) technique is used to obtain TFS, followed by using the VFCDM to obtain even… (More)

- Sheng Lu, Kihwan Ju, Ki H. Chon
- IEEE Trans. Biomed. Engineering
- 2001

A linear and nonlinear autoregressive (AR) moving average (MA) (ARMA) identification algorithm is developed for modeling time series data. The new algorithm is based on the concepts of affine geometry in which the salient feature of the algorithm is to remove the linearly dependent ARMA vectors from the pool of candidate ARMA vectors. For noiseless time… (More)

- Hengliang Wang, Kihwan Ju, Ki H Chon
- Medical engineering & physics
- 2007

The vector optimal parameter search (VOPS) and the constrained optimal parameter search (COPS) are recently developed algorithms for closed-loop linear system identification. We extend both algorithms to be applicable to a closed-loop nonlinear system, which is characterized by a vector nonlinear autoregressive model. Monte Carlo simulations of nonlinear… (More)

- Ki H. Chon, He Zhao, Rui Zou, Kihwan Ju
- IEEE Trans. Biomed. Engineering
- 2005

We extend a recently developed algorithm that expands the time-varying parameters onto a single set of basis functions, to multiple sets of basis functions. This feature allows the capability to capture many different dynamics that may be inherent in the system. A single set of basis functions that has its own unique characteristics can best capture… (More)

- Kin L. Siu, Jae M. Ann, Kihwan Ju, Myoungho Lee, Kunsoo Shin, Ki H. Chon
- IEEE Trans. Biomed. Engineering
- 2008

The bispectrum is a method to detect the presence of phase coupling between different components in a signal. The traditional way to quantify phase coupling is by means of the bicoherence index, which is essentially a normalized bispectrum. The major drawback of the bicoherence index (BCI) is that determination of significant phase coupling becomes… (More)

- Antonis A. Armoundas, Kihwan Ju, +4 authors Ki H. Chon
- Annals of Biomedical Engineering
- 2002

Current methods for detecting nonlinear determinism in a time series require long and stationary data records, as most of them assume that the observed dynamics arise only from the internal, deterministic workings of the system, and the stochastic portion of the signal (the noise component) is assumed to be negligible. To explicitly account for the… (More)

- He Zhao, Sheng Lu, Rui Zou, Kihwan Ju, Ki H. Chon
- Annals of Biomedical Engineering
- 2004

We introduce a new method to estimate reliable time-varying coherence functions (TVCF) for causal systems. The technique is based on our previously developed method to estimate time-varying transfer functions (TVTF), known as the time-varying optimal parameter search algorithm [Zou, R., H. Wang, and K. H. Chon. A robust time-varying identification algorithm… (More)