Skip to main content

Hau-Tieng Wu

Research Professor of Mathematics
Mathematics
Box 90320, Durham, NC 27708
207 Physics Building, 120 Science Drive, Durham, NC 27708

Selected Publications


When scattering transform meets non-Gaussian random processes, a double scaling limit result

Journal Article Bernoulli · August 1, 2024 Let T be a function of Hermite rank one and let {G(t)}t∈R be a mean-square continuous stationary Gaussian process with long-range dependence. We explore the finite-dimensional distributions of the second-order scattering transform of the process X = {T(G(t ... Full text Cite

Reconsider photoplethysmogram signal quality assessment in the free living environment.

Journal Article Physiological measurement · June 2024 Objective.Assessing signal quality is crucial for biomedical signal processing, yet a precise mathematical model for defining signal quality is often lacking, posing challenges for experts in labeling signal qualities. The situation is even worse in ... Full text Cite

Geometric scattering on measure spaces

Journal Article Applied and Computational Harmonic Analysis · May 1, 2024 The scattering transform is a multilayered, wavelet-based transform initially introduced as a mathematical model of convolutional neural networks (CNNs) that has played a foundational role in our understanding of these networks' stability and invariance pr ... Full text Cite

Unsupervised ensembling of multiple software sensors with phase synchronization: a robust approach for electrocardiogram-derived respiration.

Journal Article Physiological measurement · April 2024 Objective.We aimed to fuse the outputs of different electrocardiogram-derived respiration (EDR) algorithms to create one higher quality EDR signal.Methods.We viewed each EDR algorithm as a software sensor that recorded breathing activity from ... Full text Cite

Topological data analysis assisted automated sleep stage scoring using airflow signals

Journal Article Biomedical Signal Processing and Control · March 1, 2024 Objective: Breathing pattern variability (BPV), as a universal physiological feature, encodes rich health information. We aim to show that, a high-quality automatic sleep stage scoring based on a proper quantification of BPV extracting from the single airf ... Full text Cite

How do kernel-based sensor fusion algorithms behave under high-dimensional noise?

Journal Article Information and Inference · March 1, 2024 We study the behavior of two kernel based sensor fusion algorithms, nonparametric canonical correlation analysis (NCCA) and alternating diffusion (AD), under the nonnull setting that the clean datasets collected from two sensors are modeled by a common low ... Full text Cite

Removal of electrical stimulus artifact in local field potential recorded from subthalamic nucleus by using manifold denoising.

Journal Article Journal of neuroscience methods · March 2024 BackgroundDeep brain stimulation (DBS) is an effective treatment for movement disorders such as Parkinson's disease (PD). However, local field potentials (LFPs) recorded through lead externalization during high-frequency stimulation (HFS) are cont ... Full text Cite

Signal quality assessment of peripheral venous pressure.

Journal Article Journal of clinical monitoring and computing · February 2024 Develop a signal quality index (SQI) for the widely available peripheral venous pressure waveform (PVP). We focus on the quality of the cardiac component in PVP. We model PVP by the adaptive non-harmonic model. When the cardiac component in PVP is stronger ... Full text Cite

Spatiotemporal analysis using Riemannian composition of diffusion operators

Journal Article Applied and Computational Harmonic Analysis · January 1, 2024 Multivariate time-series have become abundant in recent years, as many data-acquisition systems record information through multiple sensors simultaneously. In this paper, we assume the variables pertain to some geometry and present an operator-based approa ... Full text Cite

Frequency Detection and Change Point Estimation for Time Series of Complex Oscillation

Journal Article Journal of the American Statistical Association · January 1, 2024 We consider detecting the evolutionary oscillatory pattern of a signal when it is contaminated by nonstationary noises with complexly time-varying data generating mechanism. A high-dimensional dense progressive periodogram test is proposed to accurately de ... Full text Cite

Arterial blood pressure waveform in liver transplant surgery possesses variability of morphology reflecting recipients' acuity and predicting short term outcomes.

Journal Article Journal of clinical monitoring and computing · December 2023 We investigated clinical information underneath the beat-to-beat fluctuation of the arterial blood pressure (ABP) waveform morphology. We proposed the Dynamical Diffusion Map algorithm (DDMap) to quantify the variability of morphology.  The underlying phys ... Full text Cite

Using the ear photoplethysmographic waveform as an early indicator of central hypovolemia in healthy volunteers utilizing LBNP induced hypovolemia model.

Journal Article Physiological measurement · July 2023 Objective. To study the photoplethysmographic (PPG) waveforms of different locations (ear and finger) during lower body negative pressure (LBNP) induced hypovolemia. Then, to determine whether the PPG waveform can be used to detect hypovolemia durin ... Full text Cite

Application of de-shape synchrosqueezing to estimate gait cadence from a single-sensor accelerometer placed in different body locations.

Journal Article Physiological measurement · May 2023 Objective.Commercial and research-grade wearable devices have become increasingly popular over the past decade. Information extracted from devices using accelerometers is frequently summarized as 'number of steps' (commercial devices) or 'activity c ... Full text Cite

When scattering transform meets non-Gaussian random processes, a double scaling limit result

Journal Article Bernoulli · August 1, 2024 Let T be a function of Hermite rank one and let {G(t)}t∈R be a mean-square continuous stationary Gaussian process with long-range dependence. We explore the finite-dimensional distributions of the second-order scattering transform of the process X = {T(G(t ... Full text Cite

Reconsider photoplethysmogram signal quality assessment in the free living environment.

Journal Article Physiological measurement · June 2024 Objective.Assessing signal quality is crucial for biomedical signal processing, yet a precise mathematical model for defining signal quality is often lacking, posing challenges for experts in labeling signal qualities. The situation is even worse in ... Full text Cite

Geometric scattering on measure spaces

Journal Article Applied and Computational Harmonic Analysis · May 1, 2024 The scattering transform is a multilayered, wavelet-based transform initially introduced as a mathematical model of convolutional neural networks (CNNs) that has played a foundational role in our understanding of these networks' stability and invariance pr ... Full text Cite

Unsupervised ensembling of multiple software sensors with phase synchronization: a robust approach for electrocardiogram-derived respiration.

Journal Article Physiological measurement · April 2024 Objective.We aimed to fuse the outputs of different electrocardiogram-derived respiration (EDR) algorithms to create one higher quality EDR signal.Methods.We viewed each EDR algorithm as a software sensor that recorded breathing activity from ... Full text Cite

Topological data analysis assisted automated sleep stage scoring using airflow signals

Journal Article Biomedical Signal Processing and Control · March 1, 2024 Objective: Breathing pattern variability (BPV), as a universal physiological feature, encodes rich health information. We aim to show that, a high-quality automatic sleep stage scoring based on a proper quantification of BPV extracting from the single airf ... Full text Cite

How do kernel-based sensor fusion algorithms behave under high-dimensional noise?

Journal Article Information and Inference · March 1, 2024 We study the behavior of two kernel based sensor fusion algorithms, nonparametric canonical correlation analysis (NCCA) and alternating diffusion (AD), under the nonnull setting that the clean datasets collected from two sensors are modeled by a common low ... Full text Cite

Removal of electrical stimulus artifact in local field potential recorded from subthalamic nucleus by using manifold denoising.

Journal Article Journal of neuroscience methods · March 2024 BackgroundDeep brain stimulation (DBS) is an effective treatment for movement disorders such as Parkinson's disease (PD). However, local field potentials (LFPs) recorded through lead externalization during high-frequency stimulation (HFS) are cont ... Full text Cite

Signal quality assessment of peripheral venous pressure.

Journal Article Journal of clinical monitoring and computing · February 2024 Develop a signal quality index (SQI) for the widely available peripheral venous pressure waveform (PVP). We focus on the quality of the cardiac component in PVP. We model PVP by the adaptive non-harmonic model. When the cardiac component in PVP is stronger ... Full text Cite

Spatiotemporal analysis using Riemannian composition of diffusion operators

Journal Article Applied and Computational Harmonic Analysis · January 1, 2024 Multivariate time-series have become abundant in recent years, as many data-acquisition systems record information through multiple sensors simultaneously. In this paper, we assume the variables pertain to some geometry and present an operator-based approa ... Full text Cite

Frequency Detection and Change Point Estimation for Time Series of Complex Oscillation

Journal Article Journal of the American Statistical Association · January 1, 2024 We consider detecting the evolutionary oscillatory pattern of a signal when it is contaminated by nonstationary noises with complexly time-varying data generating mechanism. A high-dimensional dense progressive periodogram test is proposed to accurately de ... Full text Cite

Arterial blood pressure waveform in liver transplant surgery possesses variability of morphology reflecting recipients' acuity and predicting short term outcomes.

Journal Article Journal of clinical monitoring and computing · December 2023 We investigated clinical information underneath the beat-to-beat fluctuation of the arterial blood pressure (ABP) waveform morphology. We proposed the Dynamical Diffusion Map algorithm (DDMap) to quantify the variability of morphology.  The underlying phys ... Full text Cite

Using the ear photoplethysmographic waveform as an early indicator of central hypovolemia in healthy volunteers utilizing LBNP induced hypovolemia model.

Journal Article Physiological measurement · July 2023 Objective. To study the photoplethysmographic (PPG) waveforms of different locations (ear and finger) during lower body negative pressure (LBNP) induced hypovolemia. Then, to determine whether the PPG waveform can be used to detect hypovolemia durin ... Full text Cite

Application of de-shape synchrosqueezing to estimate gait cadence from a single-sensor accelerometer placed in different body locations.

Journal Article Physiological measurement · May 2023 Objective.Commercial and research-grade wearable devices have become increasingly popular over the past decade. Information extracted from devices using accelerometers is frequently summarized as 'number of steps' (commercial devices) or 'activity c ... Full text Cite

CENTRAL AND NONCENTRAL LIMIT THEOREMS ARISING FROM THE SCATTERING TRANSFORM AND ITS NEURAL ACTIVATION GENERALIZATION

Journal Article SIAM Journal on Mathematical Analysis · April 1, 2023 Motivated by the analysis of complicated time series, we examine a generalization of the scattering transform that includes broad neural activation functions. This generalization is the neural activation scattering transform (NAST). NAST comprises a sequen ... Full text Cite

Numerical computation of triangular complex spherical designs with small mesh ratio

Journal Article Journal of Computational and Applied Mathematics · March 15, 2023 This paper provides triangular spherical designs for the complex unit sphere Ωd⊂ℂd by exploiting the natural correspondence with the real unit sphere S2d−1⊂R2d. A variational characterization of triangular complex designs is provided, with particular empha ... Full text Cite

Impact of Signal-to-Noise Ratio and Bandwidth on Graph Laplacian Spectrum From High-Dimensional Noisy Point Cloud

Journal Article IEEE Transactions on Information Theory · March 1, 2023 We systematically study the spectrum of kernel-based graph Laplacian (GL) constructed from high-dimensional and noisy random point cloud in the nonnull setup. The problem is motived by studying the model when the clean signal is sampled from a manifold tha ... Full text Cite

Fundamental component enhancement via adaptive nonlinear activation functions

Journal Article Applied and Computational Harmonic Analysis · March 1, 2023 In many real world oscillatory signals, the fundamental component of a signal f(t) might be weak or does not exist. This makes it difficult to estimate the instantaneous frequency of the signal. A traditional approach is to apply the rectification trick, w ... Full text Cite

Amplitude and phase measurements from harmonic analysis may lead to new physiologic insights: lower body negative pressure photoplethysmographic waveforms as an example.

Journal Article Journal of clinical monitoring and computing · February 2023 The photoplethysmographic (PPG) waveform contains hemodynamic information in its oscillations. We provide a new method for quantitative study of the waveform morphology and its relationship to the hemodynamics. A data adaptive modeling of the waveform shap ... Full text Cite

Disentangling modes with crossover instantaneous frequencies by synchrosqueezed chirplet transforms, from theory to application

Journal Article Applied and Computational Harmonic Analysis · January 1, 2023 Analysis of signals with oscillatory modes with crossover instantaneous frequencies is a challenging problem in time series analysis. One way to handle this problem is lifting the 2-dimensional time-frequency representation to a 3-dimensional representatio ... Full text Cite

An Iterative Warping and Clustering Algorithm to Estimate Multiple Wave-Shape Functions From a Nonstationary Oscillatory Signal

Journal Article IEEE Transactions on Signal Processing · January 1, 2023 Nonsinusoidal oscillatory signals are everywhere. In practice, the nonsinusoidal oscillatory pattern, modeled as a 1-periodic wave-shape function (WSF), might vary from cycle to cycle. When there are finite different WSFs, s1,sK, so that the WSF jumps from ... Full text Cite

Mutual information: Measuring nonlinear dependence in longitudinal epidemiological data.

Journal Article PLoS One · 2023 Given a large clinical database of longitudinal patient information including many covariates, it is computationally prohibitive to consider all types of interdependence between patient variables of interest. This challenge motivates the use of mutual info ... Full text Link to item Cite

Quality Aware Sleep Stage Classification over RIP Signals with Persistence Diagrams

Conference 2023 IEEE 19th International Conference on Body Sensor Networks, BSN 2023 - Proceedings · January 1, 2023 Automated sleep stage classification is a valuable tool for analyzing sleep patterns and has numerous applications in wearable healthcare systems. However, the accuracy of sleep stage classification using signals from wearable devices can be affected by da ... Full text Cite

Scalability and robustness of spectral embedding: landmark diffusion is all you need

Journal Article Information and Inference · December 1, 2022 Although spectral embedding is a widely applied dimension reduction technique in various fields, so far it is still challenging to make it scalable to handle’big data’. On the other hand, the robustness property is less explored and there exists only limit ... Full text Cite

Optimal recovery of precision matrix for Mahalanobis distance from high-dimensional noisy observations in manifold learning

Journal Article Information and Inference · December 1, 2022 Motivated by establishing theoretical foundations for various manifold learning algorithms, we study the problem of Mahalanobis distance (MD) and the associated precision matrix estimation from high-dimensional noisy data. By relying on recent transformati ... Full text Cite

Eigenvector Phase Retrieval: Recovering eigenvectors from the absolute value of their entries

Journal Article Linear Algebra and Its Applications · November 1, 2022 We consider the eigenvalue problem Ax=λx where A∈Rn×n and the eigenvalue is also real λ∈R. If we are given A, λ and, additionally, the absolute value of the entries of x (the vector (|xi|)i=1n), is there a fast way to recover x? In particular, can this be ... Full text Cite

Airflow recovery from thoracic and abdominal movements using synchrosqueezing transform and locally stationary Gaussian process regression

Journal Article Computational Statistics and Data Analysis · October 1, 2022 A wealth of information about respiratory system is encoded in the airflow signal. While direct measurement of airflow via spirometer with an occlusive seal is the gold standard, this may not be practical for ambulatory monitoring of patients. Advances in ... Full text Cite

ASYMPTOTIC ANALYSIS OF SYNCHROSQUEEZING TRANSFORM—TOWARD STATISTICAL INFERENCE WITH NONLINEAR-TYPE TIME-FREQUENCY ANALYSIS

Journal Article Annals of Statistics · October 1, 2022 We provide a statistical analysis of a tool in nonlinear-type time-frequency analysis, the synchrosqueezing transform (SST), for both the null and nonnull cases. The intricate nonlinear interaction of different quantities in SST is quantified by carefully ... Full text Cite

Convergence of graph Laplacian with kNN self-tuned kernels

Journal Article Information and Inference: A Journal of the IMA · September 8, 2022 AbstractKernelized Gram matrix $W$ constructed from data points $\{x_i\}_{i=1}^N$ as $W_{ij}= k_0( \frac{ \| x_i - x_j \|^2} {\sigma ^2} ) $ is widely used in graph-based geometric data analysis and unsuperv ... Full text Cite

RECONSIDER PHASE RECONSTRUCTION IN SIGNALS WITH DYNAMIC PERIODICITY FROM THE MODERN SIGNAL PROCESSING PERSPECTIVE

Journal Article Foundations of Data Science · September 1, 2022 Phase is the most fundamental physical quantity when we study an oscillatory time series. There have been many tools aiming to estimate phase, and most of them are developed based on the analytic function model. Unfortunately, these analytic function model ... Full text Cite

Strong uniform consistency with rates for kernel density estimators with general kernels on manifolds

Journal Article Information and Inference · June 1, 2022 When analyzing modern machine learning algorithms, we may need to handle kernel density estimation (KDE) with intricate kernels that are not designed by the user and might even be irregular and asymmetric. To handle this emerging challenge, we provide a st ... Full text Cite

Prenatal stress perturbs fetal iron homeostasis in a sex specific manner.

Journal Article Scientific reports · June 2022 The adverse effects of maternal prenatal stress (PS) on child's neurodevelopment warrant the establishment of biomarkers that enable early interventional therapeutic strategies. We performed a prospective matched double cohort study screening 2000 pregnant ... Full text Cite

Graph based Gaussian processes on restricted domains

Journal Article Journal of the Royal Statistical Society. Series B: Statistical Methodology · April 1, 2022 In nonparametric regression, it is common for the inputs to fall in a restricted subset of Euclidean space. Typical kernel-based methods that do not take into account the intrinsic geometry of the domain across which observations are collected may produce ... Full text Cite

Get rid of the beat in mobile EEG applications: A framework towards automated cardiogenic artifact detection and removal in single-channel EEG

Journal Article Biomedical Signal Processing and Control · February 1, 2022 Brain activity recordings outside clinical or laboratory settings using mobile EEG systems have gained popular interest allowing for realistic long-term monitoring and eventually leading to identification of possible biomarkers for diseases. The less obtru ... Full text Cite

Asymptotic Analysis of higher-order scattering transform of Gaussian processes

Journal Article Electronic Journal of Probability · January 1, 2022 We analyze the scattering transform with the quadratic nonlinearity (STQN) of Gaussian processes without depth limitation. STQN is a nonlinear transform that involves a sequential interlacing convolution and nonlinear operators, which is motivated to model ... Full text Cite

Robust and scalable manifold learning via landmark diffusion for long-term medical signal processing

Journal Article Journal of Machine Learning Research · January 1, 2022 Motivated by analyzing long-termphysiological time series, we design a robust and scalable spectral embedding algorithm that we refer to as RObust and Scalable Embedding via LANdmark Diffusion ( Roseland). The key is designing a diffusion process on the da ... Cite

Subthalamic high-beta oscillation informs the outcome of deep brain stimulation in patients with Parkinson's disease.

Journal Article Frontiers in human neuroscience · January 2022 BackgroundThe therapeutic effect of deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD) is related to the modulation of pathological neural activities, particularly the synchronization in the β band (1 ... Full text Cite

Extraction Algorithm for Morphologically Preserved Non-Invasive Multi-Channel Fetal ECG

Conference Computing in Cardiology · January 1, 2022 Non-invasive fetal ECG (fECG) is a promising technique that could allow low-cost and risk-free diagnosis, and long-term monitoring of fetal cardiac wellbeing. However, the low quality of the fECG extracted from non-invasive abdominal recordings hampers its ... Full text Cite

THE MANIFOLD SCATTERING TRANSFORM FOR HIGH-DIMENSIONAL POINT CLOUD DATA

Conference Proceedings of Machine Learning Research · January 1, 2022 The manifold scattering transform is a deep feature extractor for data defined on a Riemannian manifold. It is one of the first examples of extending convolutional neural network-like operators to general manifolds. The initial work on this model focused p ... Cite

WHEN RAMANUJAN MEETS TIME-FREQUENCY ANALYSIS IN COMPLICATED TIME SERIES ANALYSIS

Journal Article Pure and Applied Analysis · January 1, 2022 To handle time series with complicated oscillatory structure, we propose a novel time-frequency (TF) analysis tool that fuses the short-time Fourier transform (STFT) and periodic transform (PT). As many time series oscillate with time-varying frequency, am ... Full text Cite

Disentangling modes with crossover instantaneous frequencies by synchrosqueezed chirplet transforms, from theory to application

Journal Article · December 3, 2021 Analysis of signals with oscillatory modes with crossover instantaneous frequencies is a challenging problem in time series analysis. One way to handle this problem is lifting the 2-dimensional time-frequency representation to a 3-dimensional representatio ... Link to item Cite

Fundamental component enhancement via adaptive nonlinear activation functions

Journal Article · December 2, 2021 In many real world oscillatory signals, the fundamental component of a signal $f(t)$ might be weak or does not exist. This makes it difficult to estimate the instantaneous frequency of the signal. Traditionally, researchers apply the rectification trick, w ... Link to item Cite

On the behavior of 1-Laplacian ratio cuts on nearly rectangular domains

Journal Article Information and Inference · December 1, 2021 The p-Laplacian has attracted more and more attention in data analysis disciplines in the past decade. However, there is still a knowledge gap about its behavior, which limits its practical application. In this paper, we are interested in its iterative beh ... Full text Cite

How do kernel-based sensor fusion algorithms behave under high dimensional noise?

Journal Article · November 21, 2021 We study the behavior of two kernel based sensor fusion algorithms, nonparametric canonical correlation analysis (NCCA) and alternating diffusion (AD), under the nonnull setting that the clean datasets collected from two sensors are modeled by a common low ... Link to item Cite

Spectral convergence of graph Laplacian and heat kernel reconstruction in L from random samples

Journal Article Applied and Computational Harmonic Analysis · November 1, 2021 In the manifold setting, we provide a series of spectral convergence results quantifying how the eigenvectors and eigenvalues of the graph Laplacian converge to the eigenfunctions and eigenvalues of the Laplace-Beltrami operator in the L∞ sense. Based on t ... Full text Cite

Is the median hourly ambulatory heart rate range helpful in stratifying mortality risk among newly diagnosed atrial fibrillation patients?

Journal Article Journal of Personalized Medicine · November 1, 2021 Background: The application of heart rate variability is problematic in patients with atrial fibrillation (AF). This study aims to explore the associations between all-cause mortality and the median hourly ambulatory heart rate range (ÃHRR24hr) compared wi ... Full text Cite

Improve concentration of frequency and time (ConceFT) by novel complex spherical designs

Journal Article Applied and Computational Harmonic Analysis · September 1, 2021 Concentration of frequency and time (ConceFT) is a generalized multitaper algorithm introduced to analyze complicated non-stationary time series. To avoid the randomness in the original ConceFT algorithm, we apply the novel complex spherical design techniq ... Full text Cite

A novel feature representation approach for single-lead heartbeat classification based on adaptive Fourier decomposition

Journal Article International Journal of Wavelets, Multiresolution and Information Processing · September 1, 2021 This paper proposes a novel feature representation approach for heartbeat classification using single-lead electrocardiogram (ECG) signals based on adaptive Fourier decomposition (AFD). AFD is a recently developed signal processing tool that provides usefu ... Full text Cite

Oscillatory Biomedical Signals: Frontiers in Mathematical Models and Statistical Analysis

Journal Article Frontiers in Applied Mathematics and Statistics · July 15, 2021 Herein we describe new frontiers in mathematical modeling and statistical analysis of oscillatory biomedical signals, motivated by our recent studies of network formation in the human brain during the early stages of life and studies forty years ago on car ... Full text Cite

On Zeroes of Random Polynomials and an Application to Unwinding

Journal Article International Mathematics Research Notices · July 1, 2021 Let μ be a probability measure in C with a continuous and compactly supported density function, let z1, zn be independent random variables, zi ∼ μ, and consider the random polynomial pn(z) = ∏ k=1n(z-zk).We determine the asymptotic distribution of left z C ... Full text Open Access Cite

Fetal heart rate during maternal sleep.

Journal Article Developmental psychobiology · July 2021 Despite prolonged and cumulative exposure during gestation, little is known about the fetal response to maternal sleep. Eighty-four pregnant women with obesity (based on pre-pregnancy BMI) participated in laboratory-based polysomnography (PSG) with continu ... Full text Cite

WAVE-SHAPE OSCILLATORY MODEL FOR NONSTATIONARY PERIODIC TIME SERIES ANALYSIS

Journal Article Foundations of Data Science · June 1, 2021 The oscillations observed in many time series, particularly in biomedicine, exhibit morphological variations over time. These morphological variations are caused by intrinsic or extrinsic changes to the state of the generating system, henceforth referred t ... Full text Cite

A new approach to complicated and noisy physiological waveforms analysis: peripheral venous pressure waveform as an example.

Journal Article Journal of clinical monitoring and computing · May 2021 We introduce a recently developed nonlinear-type time-frequency analysis tool, synchrosqueezing transform (SST), to quantify complicated and noisy physiological waveform that has time-varying amplitude and frequency. We apply it to analyze a peripheral ven ... Full text Cite

Denoising click-evoked otoacoustic emission signals by optimal shrinkage.

Journal Article The Journal of the Acoustical Society of America · April 2021 Click-evoked otoacoustic emissions (CEOAEs) are clinically used as an objective way to infer whether cochlear functions are normal. However, because the sound pressure level of CEOAEs is typically much lower than the background noise, it usually takes hund ... Full text Cite

Get rid of the beat in mobile EEG applications: A framework towards automated cardiogenic artifact detection and removal in single-channel EEG

Journal Article · February 12, 2021 AbstractBrain activity recordings outside clinical or laboratory settings using mobile EEG systems have recently gained popular interest allowing for realistic long-term monitoring and eventually leading to identification o ... Full text Cite

Large-scale assessment of consistency in sleep stage scoring rules among multiple sleep centers using an interpretable machine learning algorithm.

Journal Article Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine · February 2021 Study objectivesPolysomnography is the gold standard in identifying sleep stages; however, there are discrepancies in how technicians use the standards. Because organizing meetings to evaluate this discrepancy and/or reach a consensus among multip ... Full text Cite

A Persistent Homology Approach to Heart Rate Variability Analysis With an Application to Sleep-Wake Classification.

Journal Article Frontiers in physiology · January 2021 Persistent homology is a recently developed theory in the field of algebraic topology to study shapes of datasets. It is an effective data analysis tool that is robust to noise and has been widely applied. We demonstrate a general pipeline to apply persist ... Full text Cite

On the Spectral Property of Kernel-Based Sensor Fusion Algorithms of High Dimensional Data

Journal Article IEEE Transactions on Information Theory · January 1, 2021 We apply local laws of random matrices and free probability theory to study the spectral properties of two kernel-based sensor fusion algorithms, nonparametric canonical correlation analysis (NCCA) and alternating diffusion (AD), for two simultaneously rec ... Full text Open Access Cite

Brief Report: Can a Composite Heart Rate Variability Biomarker Shed New Insights About Autism Spectrum Disorder in School-Aged Children?

Journal Article Journal of autism and developmental disorders · January 2021 Several studies show altered heart rate variability (HRV) in autism spectrum disorder (ASD), but findings are neither universal nor specific to ASD. We apply a set of linear and nonlinear HRV measures-including phase rectified signal averaging-to segments ... Full text Cite

Pattern recognition algorithm to identify detrusor overactivity on urodynamics.

Journal Article Neurourology and urodynamics · January 2021 AimsDetrusor overactivity (DO) of the bladder is a finding on urodynamic studies (UDS) that often correlates with lower urinary tract symptoms and drives management. However, UDS interpretation remains nonstandardized. We sought to develop a mathe ... Full text Cite

Cardiorespiratory coupling is associated with exercise capacity in patients with chronic obstructive pulmonary disease.

Journal Article BMC pulmonary medicine · January 2021 BackgroundThe interaction between the pulmonary function and cardiovascular mechanics is a crucial issue, particularly when treating patients with chronic obstructive pulmonary disease (COPD). Synchrogram index is a new parameter that can quantify ... Full text Cite

Interpretable morphological features for efficient single-lead automatic ventricular ectopy detection.

Journal Article J Electrocardiol · 2021 OBJECTIVE: We designed an automatic, computationally efficient, and interpretable algorithm for detecting ventricular ectopic beats in long-term, single-lead electrocardiogram recordings. METHODS: We built five simple, interpretable, and computationally ef ... Full text Link to item Cite

An Efficient Forecasting Approach to Reduce Boundary Effects in Real-Time Time-Frequency Analysis

Journal Article IEEE Transactions on Signal Processing · January 1, 2021 Time-frequency (TF) representations of time series are intrinsically subject to the boundary effects. As a result, the structures of signals that are highlighted by the representations are garbled when approaching the boundaries of the TF domain. In this p ... Full text Cite

Explore Intrinsic Geometry of Sleep Dynamics and Predict Sleep Stage by Unsupervised Learning Techniques

Chapter · January 1, 2021 We propose a novel unsupervised approach for sleep dynamics exploration and automatic annotation by combining modern harmonic analysis tools. Specifically, we apply diffusion-based algorithms, diffusion map (DM), and alternating diffusion (AD) algorithms, ... Full text Cite

Decomposing non-stationary signals with time-varying wave-shape functions

Journal Article IEEE Transactions on Signal Processing · January 1, 2021 Modern time series are usually composed of multiple oscillatory components, with time-varying frequency and amplitude contaminated by noise. The signal processing mission is further challenged if each component has an oscillatory pattern, or the wave-shape ... Full text Cite

Theta Oscillations at Subthalamic Region Predicts Hypomania State After Deep Brain Stimulation in Parkinson's Disease.

Journal Article Frontiers in human neuroscience · January 2021 Subthalamic nucleus (STN) deep brain stimulation (DBS) is an effective treatment for the motor impairments of patients with advanced Parkinson's disease. However, mood or behavioral changes, such as mania, hypomania, and impulsive disorders, can occur post ... Full text Cite

Predicting Trust Using Automated Assessment of Multivariate Interactional Synchrony

Conference Proceedings - 2021 16th IEEE International Conference on Automatic Face and Gesture Recognition, FG 2021 · January 1, 2021 Diverse disciplines are interested in how the coordination of interacting agents' movements, emotions, and physiology over time impacts social behavior. Here, we describe a new multivariate procedure for automating the investigation of this kind of behavio ... Full text Cite

Robust T-End Detection via T-End Signal Quality Index and Optimal Shrinkage.

Journal Article Sensors (Basel, Switzerland) · December 2020 An automatic accurate T-wave end (T-end) annotation for the electrocardiogram (ECG) has several important clinical applications. While there have been several algorithms proposed, their performance is usually deteriorated when the signal is noisy. Therefor ... Full text Cite

Improve Concentration of Frequency and Time (Conceft) by Novel Complex Spherical Designs

Journal Article · November 23, 2020 AbstractConcentration of frequency and time (ConceFT) is a generalized multitaper algorithm introduced to analyze complicated non-stationary time series. To avoid the randomness in the original ConceFT al ... Full text Cite

Impact of signal-to-noise ratio and bandwidth on graph Laplacian spectrum from high-dimensional noisy point cloud

Journal Article · November 21, 2020 We systematically study the spectrum of kernel-based graph Laplacian (GL) constructed from high-dimensional and noisy random point cloud in the nonnull setup. The problem is motived by studying the model when the clean signal is sampled from a manifold tha ... Link to item Cite

Non-invasive biomarkers of fetal brain development reflecting prenatal stress: An integrative multi-scale multi-species perspective on data collection and analysis.

Journal Article Neuroscience and biobehavioral reviews · October 2020 Prenatal stress (PS) impacts early postnatal behavioural and cognitive development. This process of 'fetal programming' is mediated by the effects of the prenatal experience on the developing hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous ... Full text Open Access Cite

Current state of nonlinear-type time–frequency analysis and applications to high-frequency biomedical signals

Journal Article Current Opinion in Systems Biology · October 1, 2020 Motivated by analyzing complicated time series, nonlinear-type time–frequency analysis has become an active research topic in the past decades. Those developed tools have been applied to various problems. In this article, we review those developed tools an ... Full text Cite

Accurate detection of cerebellar smooth pursuit eye movement abnormalities via mobile phone video and machine learning.

Journal Article Scientific reports · October 2020 Eye movements are disrupted in many neurodegenerative diseases and are frequent and early features in conditions affecting the cerebellum. Characterizing eye movements is important for diagnosis and may be useful for tracking disease progression and respon ... Full text Cite

Portable Sleep Apnea Syndrome Screening and Event Detection Using Long Short-Term Memory Recurrent Neural Network.

Journal Article Sensors (Basel, Switzerland) · October 2020 Obstructive sleep apnea/hypopnea syndrome (OSAHS) is characterized by repeated airflow partial reduction or complete cessation due to upper airway collapse during sleep. OSAHS can induce frequent awake and intermittent hypoxia that is associated with hyper ... Full text Cite

Differentiation of skin incision and laparoscopic trocar insertion via quantifying transient bradycardia measured by electrocardiogram.

Journal Article Journal of clinical monitoring and computing · August 2020 Most surgical procedures involve structures deeper than the skin. However, the difference in surgical noxious stimulation between skin incision and laparoscopic trocar insertion is unknown. By analyzing instantaneous heart rate (IHR) calculated from the el ... Full text Cite

Unsupervised Ensembling of Multiple Software Sensors with Phase Synchronization: A Robust Approach For Electrocardiogram-derived Respiration

Journal Article · June 23, 2020 Objective: We aimed to fuse the outputs of different electrocardiogram-derived respiration (EDR) algorithms to create one EDR signal that is of higher quality. Methods: We viewed each EDR algorithm as a software sensor that recorded breathing activity from ... Link to item Cite

Convergence analysis of Adaptive Locally Iterative Filtering and SIFT method

Journal Article · May 10, 2020 Adaptive Local Iterative Filtering (ALIF) is a currently proposed novel time-frequency analysis tool. It has been empirically shown that ALIF is able to separate components and overcome the mode-mixing problem. However, so far its convergence is still an o ... Link to item Cite

An adaptive QRS detection algorithm for ultra-long-term ECG recordings.

Journal Article Journal of electrocardiology · May 2020 BackgroundAccurate detection of QRS complexes during mobile, ultra-long-term ECG monitoring is challenged by instances of high heart rate, dramatic and persistent changes in signal amplitude, and intermittent deformations in signal quality that ar ... Full text Cite

Novel Imaging Revealing Inner Dynamics for Cardiovascular Waveform Analysis via Unsupervised Manifold Learning.

Journal Article Anesthesia and analgesia · May 2020 BackgroundCardiovascular waveforms contain information for clinical diagnosis. By learning and organizing the subtle change of waveform morphology from large amounts of raw waveform data, unsupervised manifold learning helps delineate a high-dimen ... Full text Cite

Save Muscle Information-Unfiltered EEG Signal Helps Distinguish Sleep Stages.

Journal Article Sensors (Basel, Switzerland) · April 2020 Based on the well-established biopotential theory, we hypothesize that the high frequency spectral information, like that higher than 100Hz, of the EEG signal recorded in the off-the-shelf EEG sensor contains muscle tone information. We show that an existi ... Full text Cite

When Ramanujan meets time-frequency analysis in complicated time series analysis

Journal Article Pure Appl. Analysis · March 31, 2020 To handle time series with complicated oscillatory structure, we propose a novel time-frequency (TF) analysis tool that fuses the short time Fourier transform (STFT) and periodic transform (PT). Since many time series oscillate with time-varying frequency, ... Link to item Cite

Transient-evoked otoacoustic emission signals predicting outcomes of acute sensorineural hearing loss in patients with Ménière's disease.

Journal Article Acta oto-laryngologica · March 2020 Background: Fluctuating hearing loss is characteristic of Ménière's disease (MD) during acute episodes. However, no reliable audiometric hallmarks are available for counselling the hearing recovery possibility.Aims/objectives: To find paramet ... Full text Cite

Hypoventilation patterns during bronchoscopic sedation and their clinical relevance based on capnographic and respiratory impedance analysis.

Journal Article Journal of clinical monitoring and computing · February 2020 Capnography involves the measurement of end-tidal CO2 (EtCO2) values to detect hypoventilation in patients undergoing sedation. In a previous study, we reported that initiating a flexible bronchoscopy (FB) examination only after detec ... Full text Cite

Fetal heart rate variability responsiveness to maternal stress, non-invasively detected from maternal transabdominal ECG.

Journal Article Archives of gynecology and obstetrics · February 2020 PurposePrenatal stress (PS) during pregnancy affects in utero- and postnatal child brain-development. Key systems affected are the hypothalamic-pituitary-adrenal axis and the autonomic nervous system (ANS). Maternal- and fetal ANS activity can be ... Full text Cite

Diffuse to fuse EEG spectra – Intrinsic geometry of sleep dynamics for classification

Journal Article Biomedical Signal Processing and Control · January 1, 2020 We propose a novel algorithm for sleep dynamics visualization and automatic annotation by applying diffusion geometry based sensor fusion algorithm to fuse spectral information from two electroencephalograms (EEG). The diffusion geometry approach helps org ... Full text Cite

Solving Jigsaw Puzzles by the Graph Connection Laplacian

Journal Article SIAM Journal on Imaging Sciences · January 2020 Full text Cite

Robust and scalable manifold learning via landmark diffusion for long-term medical signal processing

Journal Article · 2020 Motivated by analyzing long-term physiological time series, we design a robust and scalable spectral embedding algorithm, coined the algorithm RObust and Scalable Embedding via LANdmark Diffusion (ROSE-LAND). The key is designing a diffusion process on the ... Full text Cite

Reconsider phase reconstruction in signals with dynamic periodicity from the modern signal processing perspective

Journal Article · 2020 Phase is the most fundamental physical quantity when we study an oscillatory time series. There are many tools aiming to estimate phase, most of them are developed based on the analytic function model. Unfortunately, this approach might not be suitable for ... Full text Cite

Recovery of the fetal electrocardiogram for morphological analysis from two trans-abdominal channels via optimal shrinkage.

Journal Article Physiol Meas · December 2, 2019 OBJECTIVE: We propose a novel algorithm to recover fetal electrocardiogram (ECG) for both the fetal heart rate analysis and morphological analysis of its waveform from two or three trans-abdominal maternal ECG channels. APPROACH: We design an algorithm bas ... Full text Link to item Cite

Locally convex kernel mixtures: Bayesian subspace learning

Conference Proceedings - 18th IEEE International Conference on Machine Learning and Applications, ICMLA 2019 · December 1, 2019 Kernel mixture models are routinely used for density estimation. However, in multivariate settings, issues arise in efficiently approximating lower-dimensional structure in the data. For example, it is common to suppose that the density is concentrated nea ... Full text Cite

Latent common manifold learning with alternating diffusion: Analysis and applications

Journal Article Applied and Computational Harmonic Analysis · November 1, 2019 The analysis of data sets arising from multiple sensors has drawn significant research attention over the years. Traditional methods, including kernel-based methods, are typically incapable of capturing nonlinear geometric structures. We introduce a latent ... Full text Cite

A healthy dose of chaos: Using fractal frameworks for engineering higher-fidelity biomedical systems.

Journal Article Biomaterials · October 2019 Optimal levels of chaos and fractality are distinctly associated with physiological health and function in natural systems. Chaos is a type of nonlinear dynamics that tends to exhibit seemingly random structures, whereas fractality is a measure of the exte ... Full text Cite

Non-Contact Photoplethysmogram and Instantaneous Heart Rate Estimation from Infrared Face Video

Conference Proceedings - International Conference on Image Processing, ICIP · September 1, 2019 Extracting the instantaneous heart rate (iHR) from face videos has been well studied in recent years. It is well known that changes in skin color due to blood flow can be captured using conventional cameras. One of the main limitations of methods that rely ... Full text Cite

Numerical computation of triangular complex spherical designs with small mesh ratio

Journal Article · July 31, 2019 This paper provides triangular spherical designs for the complex unit sphere $\Omega^d$ by exploiting the natural correspondence between the complex unit sphere in $d$ dimensions and the real unit sphere in $2d-1$. The existence of triangular and square co ... Link to item Cite

Recycling cardiogenic artifacts in impedance pneumography

Journal Article Biomedical Signal Processing and Control · May 1, 2019 Purpose: Biomedical sensors often exhibit cardiogenic artifacts which, while distorting the signal of interest, carry useful hemodynamic information. We propose an algorithm to remove and extract hemodynamic information from these cardiogenic artifacts. Me ... Full text Cite

Asymptotic analysis of synchrosqueezing transform -- toward statistical inference with nonlinear-type time-frequency analysis

Journal Article · April 20, 2019 We provide a statistical analysis of a tool in nonlinear-type time-frequency analysis, the synchrosqueezing transform (SST), for both the null and non-null cases. The intricate nonlinear interaction of different quantities in SST is quantified by carefully ... Link to item Cite

Optimal Recovery of Precision Matrix for Mahalanobis Distance from High Dimensional Noisy Observations in Manifold Learning

Journal Article · April 19, 2019 Motivated by establishing theoretical foundations for various manifold learning algorithms, we study the problem of Mahalanobis distance (MD), and the associated precision matrix, estimation from high-dimensional noisy data. By relying on recent transforma ... Link to item Cite

A new test for functional one-way ANOVA with applications to ischemic heart screening

Journal Article Computational Statistics and Data Analysis · April 1, 2019 Motivated by an ischemic heart screening problem, a new global test for one-way ANOVA in functional data analysis is studied. The test statistic is taken as the maximum of the pointwise F-test statistic over the interval the functional responses are observ ... Full text Cite

Traditional Chinese medicine use is associated with lower end-stage renal disease and mortality rates among patients with diabetic nephropathy: a population-based cohort study.

Journal Article BMC complementary and alternative medicine · April 2019 BackgroundDiabetic nephropathy (DN) is a common complication of diabetes mellitus (DM) that imposes an enormous burden on the healthcare system. Although some studies show that traditional Chinese medicine (TCM) treatments confer a protective effe ... Full text Cite

A Novel Blaschke Unwinding Adaptive-Fourier-Decomposition-Based Signal Compression Algorithm With Application on ECG Signals.

Journal Article IEEE journal of biomedical and health informatics · March 2019 This paper presents a novel signal compression algorithm based on the Blaschke unwinding adaptive Fourier decomposition (AFD). The Blaschke unwinding AFD is a newly developed signal decomposition theory. It utilizes the Nevanlinna factorization and the max ... Full text Cite

Alternating diffusion maps for multimodal data fusion

Journal Article Information Fusion · January 1, 2019 The problem of information fusion from multiple data-sets acquired by multimodal sensors has drawn significant research attention over the years. In this paper, we focus on a particular problem setting consisting of a physical phenomenon or a system of int ... Full text Cite

Unexpected sawtooth artifact in beat-to-beat pulse transit time measured from patient monitor data.

Journal Article PloS one · January 2019 ObjectIt is increasingly popular to collect as much data as possible in the hospital setting from clinical monitors for research purposes. However, in this setup the data calibration issue is often not discussed and, rather, implicitly assumed, wh ... Full text Cite

Diffusion operators for multimodal data analysis

Journal Article · January 1, 2019 In this chapter, we present a Manifold Learning viewpoint on the analysis of data arising from multiple modalities. We assume that the high-dimensional multimodal data lie on underlying low-dimensional manifolds and devise a new data-driven representation ... Full text Cite

CONNECTING DOTS: FROM LOCAL COVARIANCE TO EMPIRICAL INTRINSIC GEOMETRY AND LOCALLY LINEAR EMBEDDING

Journal Article Pure and Applied Analysis · January 1, 2019 Local covariance structure under the manifold setup has been widely applied in the machine-learning community. Based on the established theoretical results, we provide an extensive study of two relevant manifold learning algorithms, empirical intrinsic geo ... Full text Cite

Meniere's disease prognosis by learning from transient-evoked otoacoustic emission signals

Conference Proceedings of the International Congress on Acoustics · January 1, 2019 Accurate prognosis of Meniere's disease (MD) is difficult. The aim of this study is to treat it as a machine-learning problem through the analysis of transient-evoked (TE) otoacoustic emission (OAE) data obtained from MD patients. Thirty-three patients who ... Full text Cite

Recovering Hidden Components in Multimodal Data with Composite Diffusion Operators

Journal Article SIAM Journal on Mathematics of Data Science · January 2019 Full text Cite

Embeddings of Riemannian manifolds with finite eigenvector fields of connection Laplacian

Journal Article Calculus of Variations and Partial Differential Equations · October 1, 2018 We study the problem asking if one can embed manifolds into finite dimensional Euclidean spaces by taking finite number of eigenvector fields of the connection Laplacian. This problem is essential for the dimension reduction problem in manifold learning. I ... Full text Cite

A Comparison of Five Algorithms for Fetal Magnetocardiography Signal Extraction.

Journal Article Cardiovascular engineering and technology · September 2018 Fetal magnetocardiography (fMCG) provides accurate and reliable measurements of electrophysiological events in the fetal heart and is capable of studying fetuses with congenital heart diseases. A variety of techniques exist to extract the fMCG signal with ... Full text Cite

Sleep-wake classification via quantifying heart rate variability by convolutional neural network.

Journal Article Physiological measurement · August 2018 ObjectiveFluctuations in heart rate are intimately related to changes in the physiological state of the organism. We exploit this relationship by classifying a human participant's wake/sleep status using his instantaneous heart rate (IHR) series.< ... Full text Cite

Erratum: Validation of the Name Paraphlomis hispida (Lamiaceae) (Novon (2017) 25 (436-437) DOI: 10.3417/D-16-00022)

Journal Article Novon · August 1, 2018 The name Paraphlomis hispida C. Y. Wu (Lamiaceae) was not initially validly published due to the author's failure to select a single type. Lin et al. published a validation of this name in Novon, Vol. 25 (2017: 436-437), designating C. W. Wang 83872 (PE) a ... Full text Cite

Phenotype-based and self-learning inter-individual sleep apnea screening with a level IV-like monitoring system

Journal Article Frontiers in Physiology · July 2, 2018 Purpose: We propose a phenotype-based artificial intelligence system that can self-learn and is accurate for screening purposes and test it on a Level IV-like monitoring system. Methods: Based on the physiological knowledge, we hypothesize that the phenoty ... Full text Cite

Analyzing transient-evoked otoacoustic emissions by concentration of frequency and time.

Journal Article The Journal of the Acoustical Society of America · July 2018 The linear part of transient evoked otoacoustic emission (TEOAE) is thought to be generated via coherent reflection near the characteristic place of constituent wave components. Because of the tonotopic organization of the cochlea, high frequency emissions ... Full text Cite

Manifold Learning via the Principle Bundle Approach

Journal Article Frontiers in Applied Mathematics and Statistics · June 25, 2018 In this paper, we propose a novel principal bundle model and apply it to the image denoising problem. This model is based on the fact that the patch manifold admits canonical groups actions such as rotation. We introduce an image denoising algorithm, calle ... Full text Cite

Analysis of click-evoked otoacoustic emissions by concentration of frequency and time: Preliminary results from normal hearing and Ménière's disease ears

Conference AIP Conference Proceedings · May 31, 2018 The presence of click-evoked (CE) otoacoustic emissions (OAEs) has been clinically accepted as an indicator of normal cochlear processing of sounds. For treatment and diagnostic purposes, however, clinicians do not typically pay attention to the detailed s ... Full text Open Access Cite

A new approach for analysis of heart rate variability and QT variability in long-term ECG recording.

Journal Article Biomedical engineering online · May 2018 Background and purposeWith the emergence of long-term electrocardiogram (ECG) recordings that extend several days beyond the typical 24-48 h, the development of new tools to measure heart rate variability (HRV) and QT variability is needed to util ... Full text Cite

A Portable Monitoring System with Automatic Event Detection for Sleep Apnea Level-IV Evaluation

Conference Proceedings - IEEE International Symposium on Circuits and Systems · April 26, 2018 To meet the demands on a comfortable screening, or even diagnostic, equipment without interfering with the sleep, this study develops a level IV portable system, equipped with two tri-axial accelerometers (TAA) measuring the thoracic and abdominal respirat ... Full text Cite

Wave-Shape Function Analysis: When Cepstrum Meets Time–Frequency Analysis

Journal Article Journal of Fourier Analysis and Applications · April 1, 2018 We propose to combine cepstrum and nonlinear time–frequency (TF) analysis to study multiple component oscillatory signals with time-varying frequency and amplitude and with time-varying non-sinusoidal oscillatory pattern. The concept of cepstrum is applied ... Full text Cite

Non-invasive acquisition of fetal ECG from the maternal xyphoid process: a feasibility study in pregnant sheep and a call for open data sets.

Journal Article Physiological measurement · March 2018 ObjectiveThe utility of fetal heart rate (FHR) monitoring can only be achieved with an acquisition sampling rate that preserves the underlying physiological information on the millisecond time scale (1000 Hz rather than 4 Hz). For such acquisition ... Full text Cite

Convex Optimization approach to signals with fast varying instantaneous frequency

Journal Article Applied and Computational Harmonic Analysis · January 1, 2018 Motivated by the limitation of analyzing oscillatory signals composed of multiple components with fast-varying instantaneous frequency, we approach the time-frequency analysis problem by optimization. Based on the proposed adaptive harmonic model, the time ... Full text Cite

Sleep Apnea Detection Based on Thoracic and Abdominal Movement Signals of Wearable Piezoelectric Bands

Journal Article IEEE Journal of Biomedical and Health Informatics · November 1, 2017 Physiologically, the thoracic (THO) and abdominal (ABD) movement signals, captured using wearable piezoelectric bands, provide information about various types of apnea, including central sleep apnea (CSA) and obstructive sleep apnea (OSA). However, the use ... Full text Cite

Feasibility of Classifying Life Stages and Searching for the Determinants: Results from the Medical Expenditure Panel Survey 1996–2011

Journal Article Frontiers in Public Health · October 27, 2017 Background: Life stages are not clearly defined and significant determinants for the identification of stages are not discussed. This study aims to test a data-driven approach to define stages and to identify the major determinants. Methods: This study ana ... Full text Cite

Capnography monitoring the hypoventilation during the induction of bronchoscopic sedation: A randomized controlled trial.

Journal Article Scientific reports · August 2017 We hypothesize that capnography could detect hypoventilation during induction of bronchoscopic sedation and starting bronchoscopy following hypoventilation, may decrease hypoxemia. Patients were randomized to: starting bronchoscopy when hypoventilation (hy ... Full text Open Access Cite

A network perspective on patient experiences and health status: the Medical Expenditure Panel Survey 2004 to 2011.

Journal Article BMC health services research · August 2017 BackgroundThere is a growing emphasis on the need to engage patients in order to improve the quality of health care and improve health outcomes. However, we are still lacking a comprehensive understanding on how different measures of patient exper ... Full text Cite

An exploration algorithm for stochastic simulators driven by energy gradients

Journal Article Entropy · July 1, 2017 In recent work, we have illustrated the construction of an exploration geometry on free energy surfaces: the adaptive computer-assisted discovery of an approximate low-dimensional manifold on which the effective dynamics of the system evolves. Constructing ... Full text Cite

Entropy-based time-varying window width selection for nonlinear-type time–frequency analysis

Journal Article International Journal of Data Science and Analytics · June 1, 2017 We propose a time-varying optimal window width (TVOWW) and an adaptive optimal window width selection schemes to optimize the performance of several nonlinear-type time–frequency analyses, including the reassignment method and its variations. A window rend ... Full text Cite

Single-lead f-wave extraction using diffusion geometry.

Journal Article Physiological measurement · June 2017 ObjectiveA novel single-lead f-wave extraction algorithm based on the modern diffusion geometry data analysis framework is proposed.ApproachThe algorithm is essentially an averaged beat subtraction algorithm, where the ventricular activit ... Full text Cite

Extract Fetal ECG from Single-Lead Abdominal ECG by De-Shape Short Time Fourier Transform and Nonlocal Median

Journal Article Frontiers in Applied Mathematics and Statistics · February 22, 2017 The multiple fundamental frequency detection problem and the source separation problem from a single-channel signal containing multiple oscillatory components and a nonstationary noise are both challenging tasks. To extract the fetal electrocardiogram (ECG ... Full text Cite

Heart beat classification from single-lead ECG using the synchrosqueezing transform.

Journal Article Physiological measurement · February 2017 The processing of ECG signal provides a wealth of information on cardiac function and overall cardiovascular health. While multi-lead ECG recordings are often necessary for a proper assessment of cardiac rhythms, they are not always available or practical, ... Full text Cite

The correlation between pulse diagnosis and constitution identification in traditional Chinese medicine.

Journal Article Complementary therapies in medicine · February 2017 ObjectivesOur study aimed to correlate pulse wave parameters such as augmentation index (AI) and heart rate variability with traditional Chinese medicine (TCM) constitution for evaluating health status.DesignOut of 177 subjects, 69 health ... Full text Cite

Embedding Riemannian manifolds by the heat kernel of the connection Laplacian

Journal Article Advances in Mathematics · January 2, 2017 Given a class of closed Riemannian manifolds with prescribed geometric conditions, we introduce an embedding of the manifolds into ℓ2 based on the heat kernel of the Connection Laplacian associated with the Levi-Civita connection on the tangent bundle. As ... Full text Cite

ConceFT for Time-Varying Heart Rate Variability Analysis as a Measure of Noxious Stimulation During General Anesthesia.

Journal Article IEEE transactions on bio-medical engineering · January 2017 ObjectiveHeart rate variability (HRV) offers a noninvasive way to peek into the physiological status of the human body. When this physiological status is dynamic, traditional HRV indices calculated from power spectrum do not resolve the dynamic si ... Full text Cite

Efficient Fetal-Maternal ECG Signal Separation from Two Channel Maternal Abdominal ECG via Diffusion-Based Channel Selection.

Journal Article Frontiers in physiology · January 2017 There is a need for affordable, widely deployable maternal-fetal ECG monitors to improve maternal and fetal health during pregnancy and delivery. Based on the diffusion-based channel selection, here we present the mathematical formalism and clinical valida ... Full text Open Access Cite

How Nonlinear-Type Time-Frequency Analysis Can Help in Sensing Instantaneous Heart Rate and Instantaneous Respiratory Rate from Photoplethysmography in a Reliable Way.

Journal Article Frontiers in physiology · January 2017 Despite the population of the noninvasive, economic, comfortable, and easy-to-install photoplethysmography (PPG), it is still lacking a mathematically rigorous and stable algorithm which is able to simultaneously extract from a single-channel PPG signal th ... Full text Open Access Cite

Prediction of the severity of obstructive sleep apnea by anthropometric features via support vector machine.

Journal Article PloS one · January 2017 To develop an applicable prediction for obstructive sleep apnea (OSA) is still a challenge in clinical practice. We apply a modern machine learning method, the support vector machine to establish a predicting model for the severity of OSA. The support vect ... Full text Cite

Spectral convergence of the connection Laplacian from random samples

Journal Article Information and Inference · January 1, 2017 Spectral methods that are based on eigenvectors and eigenvalues of discrete graph Laplacians, such as Diffusion Maps and Laplacian Eigenmaps, are often used for manifold learning and nonlinear dimensionality reduction. Itwas previously shown by Belkin & Ni ... Full text Cite

Alternating projection, ptychographic imaging and phase synchronization

Journal Article Applied and Computational Harmonic Analysis · November 1, 2016 We demonstrate necessary and sufficient conditions of the local convergence of the alternating projection algorithm to a unique solution up to a global phase factor. Additionally, for the ptychography imaging problem, we discuss phase synchronization and g ... Full text Cite

Imaging Cytometry of Human Leukocytes with Third Harmonic Generation Microscopy.

Journal Article Scientific reports · November 2016 Based on third-harmonic-generation (THG) microscopy and a k-means clustering algorithm, we developed a label-free imaging cytometry method to differentiate and determine the types of human leukocytes. According to the size and average intensity of cells in ... Full text Open Access Cite

Optimizing Estimates of Instantaneous Heart Rate from Pulse Wave Signals with the Synchrosqueezing Transform.

Journal Article Methods of information in medicine · October 2016 BackgroundWith recent advances in sensor and computer technologies, the ability to monitor peripheral pulse activity is no longer limited to the laboratory and clinic. Now inexpensive sensors, which interface with smartphones or other computer-bas ... Full text Cite

When Interpolation-Induced Reflection Artifact Meets Time-Frequency Analysis.

Journal Article IEEE transactions on bio-medical engineering · October 2016 ObjectiveWhile extracting the temporal dynamical features based on the time-frequency analyses, like the reassignment and synchrosqueezing transform, attracts more and more interest in biomedical data analysis, we should be careful about artifacts ... Full text Cite

Electrocardiographic J Wave and Cardiovascular Outcomes in the General Population (from the Atherosclerosis Risk In Communities Study).

Journal Article The American journal of cardiology · September 2016 The association between the J wave, a key component of the early repolarization pattern, and adverse cardiovascular outcomes remains unclear. Inconsistencies have stemmed from the different methods used to measure the J wave. We examined the association be ... Full text Open Access Cite

Real-Time dynamics acquisition from irregular samples-With application to anesthesia evaluation

Journal Article Analysis and Applications · July 1, 2016 Although most digital representations of information sources are obtained by uniform sampling of some continuous function representations, there are many important events for which only irregular data samples are available, including trading data of the fi ... Full text Cite

ConceFT: concentration of frequency and time via a multitapered synchrosqueezed transform.

Journal Article Philosophical transactions. Series A, Mathematical, physical, and engineering sciences · April 2016 A new method is proposed to determine the time-frequency content of time-dependent signals consisting of multiple oscillatory components, with time-varying amplitudes and instantaneous frequencies. Numerical experiments as well as a theoretical analysis ar ... Full text Cite

Graph connection Laplacian methods can be made robust to noise

Journal Article Annals of Statistics · February 1, 2016 Recently, several data analytic techniques based on graph connection Laplacian (GCL) ideas have appeared in the literature. At this point, the properties of these methods are starting to be understood in the setting where the data is observed without noise ... Full text Cite

Modeling the Pulse Signal by Wave-Shape Function and Analyzing by Synchrosqueezing Transform.

Journal Article PloS one · January 2016 We apply the recently developed adaptive non-harmonic model based on the wave-shape function, as well as the time-frequency analysis tool called synchrosqueezing transform (SST) to model and analyze oscillatory physiological signals. To demonstrate how the ... Full text Cite

Temporal Patterns in Sheep Fetal Heart Rate Variability Correlate to Systemic Cytokine Inflammatory Response: A Methodological Exploration of Monitoring Potential Using Complex Signals Bioinformatics.

Journal Article PloS one · January 2016 Fetal inflammation is associated with increased risk for postnatal organ injuries. No means of early detection exist. We hypothesized that systemic fetal inflammation leads to distinct alterations of fetal heart rate variability (fHRV). We tested this hypo ... Full text Cite

Non-parametric estimation of intraday spot volatility: Disentangling instantaneous trend and seasonality

Journal Article Econometrics · December 1, 2015 We provide a new framework for modeling trends and periodic patterns in high-frequency financial data. Seeking adaptivity to ever-changing market conditions, we enlarge the Fourier flexible form into a richer functional class: both our smooth trend and the ... Full text Cite

Exploring laser-driven quantum phenomena from a time-frequency analysis perspective: a comprehensive study.

Journal Article Optics express · November 2015 Time-frequency (TF) analysis is a powerful tool for exploring ultrafast dynamics in atoms and molecules. While some TF methods have demonstrated their usefulness and potential in several quantum systems, a systematic comparison among them is still lacking. ... Full text Cite

Alternating diffusion for common manifold learning with application to sleep stage assessment

Conference ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings · August 4, 2015 In this paper, we address the problem of multimodal signal processing and present a manifold learning method to extract the common source of variability from multiple measurements. This method is based on alternating-diffusion and is particularly adapted t ... Full text Cite

Assess sleep stage by modern signal processing techniques.

Journal Article IEEE transactions on bio-medical engineering · April 2015 In this paper, two modern adaptive signal processing techniques, empirical intrinsic geometry and synchrosqueezing transform, are applied to quantify different dynamical features of the respiratory and electroencephalographic signals. We show that the prop ... Full text Cite

Graph connection Laplacian and random matrices with random blocks

Journal Article Information and Inference · March 1, 2015 Graph connection Laplacian (GCL) is a modern data analysis technique that is starting to be applied for the analysis of high-dimensional and massive datasets. Motivated by this technique, we study matrices that are akin to the ones appearing in the null ca ... Full text Cite

Respiratory variability during NAVA ventilation in children: Authors' reply

Journal Article Frontiers in Pediatrics · February 1, 2015 Full text Cite

Automated J wave detection from digital 12-lead electrocardiogram.

Journal Article Journal of electrocardiology · January 2015 In this report we provide a method for automated detection of J wave, defined as a notch or slur in the descending slope of the terminal positive wave of the QRS complex, using signal processing and functional data analysis techniques. Two different sets o ... Full text Cite

ALTERNATING DIFFUSION FOR COMMON MANIFOLD LEARNING WITH APPLICATION TO SLEEP STAGE ASSESSMENT

Conference 2015 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING (ICASSP) · 2015 Cite

A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform

Journal Article AIP Advances · November 1, 2014 This study introduces a new adaptive time-frequency (TF) analysis technique, the synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an ab initio level, upon which we have demonstrated its versatility as a new viabl ... Full text Cite

Impact of ventilatory modes on the breathing variability in mechanically ventilated infants

Journal Article Frontiers in Pediatrics · November 1, 2014 Objectives: Reduction of breathing variability is associated with adverse outcome. During mechanical ventilation, the variability of ventilatory pressure is dependent on the ventilatory mode. During neurally adjusted ventilatory assist (NAVA), the support ... Full text Cite

Evaluating physiological dynamics via synchrosqueezing: prediction of ventilator weaning.

Journal Article IEEE transactions on bio-medical engineering · March 2014 Oscillatory phenomena abound in many types of signals. Identifying the individual oscillatory components that constitute an observed biological signal leads to profound understanding about the biological system. The instantaneous frequency (IF), the amplit ... Full text Cite

Using synchrosqueezing transform to discover breathing dynamics from ECG signals

Journal Article Applied and Computational Harmonic Analysis · March 1, 2014 The acquisition of breathing dynamics without directly recording the respiratory signals is beneficial in many clinical settings. The electrocardiography (ECG)-derived respiration (EDR) algorithm enables data acquisition in this manner. However, the EDR al ... Full text Cite

Time-varying spectral analysis revealing differential effects of sevoflurane anaesthesia: non-rhythmic-to-rhythmic ratio.

Journal Article Acta anaesthesiologica Scandinavica · February 2014 BackgroundHeart rate variability (HRV) may reflect various physiological dynamics. In particular, variation of R-R peak interval (RRI) of electrocardiography appears regularly oscillatory in deeper levels of anaesthesia and less regular in lighter ... Full text Cite

Non-parametric and adaptive modelling of dynamic periodicity and trend with heteroscedastic and dependent errors

Journal Article Journal of the Royal Statistical Society. Series B: Statistical Methodology · January 1, 2014 Periodicity and trend are features describing an observed sequence, and extracting these features is an important issue in many scientific fields. However, it is not an easy task for existing methods to analyse simultaneously the trend and dynamics of the ... Full text Cite

Augmented projections for ptychographic imaging

Journal Article Inverse Problems · November 1, 2013 Ptychography is a popular technique to achieve diffraction limited resolution images of a two- or three-dimensional sample using high frame rate detectors. We introduce a relaxation of common projection algorithms to account for instabilities given by inte ... Full text Cite

A New Test for One-Way ANOVA with Functional Data and Application to Ischemic Heart Screening

Journal Article · September 27, 2013 We propose and study a new global test, namely the $F_{\max}$-test, for the one-way ANOVA problem in functional data analysis. The test statistic is taken as the maximum value of the usual pointwise $F$-test statistics over the interval the functional resp ... Link to item Cite

Instantaneous frequency and wave shape functions (I)

Journal Article Applied and Computational Harmonic Analysis · September 1, 2013 Although one can formulate an intuitive notion of instantaneous frequency, generalizing "frequency" as we understand it in e.g. the Fourier transform, a rigorous mathematical definition is lacking. In this paper, we consider a class of functions composed o ... Full text Cite

The Synchrosqueezing algorithm for time-varying spectral analysis: Robustness properties and new paleoclimate applications

Journal Article Signal Processing · May 1, 2013 We analyze the stability properties of the Synchrosqueezing transform, a time-frequency signal analysis method that can identify and extract oscillatory components with time-varying frequency and amplitude. We show that Synchrosqueezing is robust to bounde ... Full text Cite

Local linear regression on manifolds and its geometric interpretation

Journal Article Journal of the American Statistical Association · January 1, 2013 High-dimensional data analysis has been an active area, and the main focus areas have been variable selection and dimension reduction. In practice, it occurs often that the variables are located on an unknown, lower-dimensional nonlinear manifold. Under th ... Full text Cite

Time-frequency reassignment and synchrosqueezing: An overview

Journal Article IEEE Signal Processing Magazine · January 1, 2013 This article provides a general overview of time-frequency (T-F) reassignment and synchrosqueezing techniques applied to multicomponent signals, covering the theoretical background and applications. We explain how synchrosqueezing can be viewed as a specia ... Full text Cite

Heart rate variability is associated with survival in patients with brain metastasis: a preliminary report.

Journal Article BioMed research international · January 2013 Impaired heart rate variability (HRV) has been demonstrated as a negative survival prognosticator in various diseases. We conducted this prospective study to evaluate how HRV affects brain metastasis (BM) patients. Fifty-one BM patients who had not undergo ... Full text Open Access Cite

Two-Dimensional Tomography from Noisy Projections Taken at Unknown Random Directions.

Journal Article SIAM journal on imaging sciences · January 2013 Computerized tomography is a standard method for obtaining internal structure of objects from their projection images. While CT reconstruction requires the knowledge of the imaging directions, there are some situations in which the imaging directions are u ... Full text Cite

Vector Diffusion Maps and the Connection Laplacian.

Journal Article Communications on pure and applied mathematics · August 2012 We introduce vector diffusion maps (VDM), a new mathematical framework for organizing and analyzing massive high-dimensional data sets, images, and shapes. VDM is a mathematical and algorithmic generalization of diffusion maps and other nonlinear di ... Full text Cite

Synchrosqueezing-based recovery of instantaneous frequency from nonuniform samples

Journal Article SIAM Journal on Mathematical Analysis · November 21, 2011 We propose a new approach for studying the notion of the instantaneous frequency of a signal. We build on ideas from the Synchrosqueezing theory of Daubechies, Lu, andWu [Appl. Comput. Harmonic Anal., 30 (2010), pp. 243-261] and consider a variant of Synch ... Full text Cite

Orientability and Diffusion Maps.

Journal Article Applied and computational harmonic analysis · July 2011 One of the main objectives in the analysis of a high dimensional large data set is to learn its geometric and topological structure. Even though the data itself is parameterized as a point cloud in a high dimensional ambient space ℝ(p), the correlation bet ... Full text Cite

One or two frequencies? the synchrosqueezing answers

Journal Article Advances in Adaptive Data Analysis · April 1, 2011 The synchrosqueezed transform was proposed recently in [Daubechies et al. (2009)] as an alternative to the empirical mode decomposition (EMD) [Huang et al. (1998)], to decompose composite signals into a sum of "modes" that each have well-defined instantane ... Full text Cite

Synchrosqueezed wavelet transforms: An empirical mode decomposition-like tool

Journal Article Applied and Computational Harmonic Analysis · March 2011 Full text Cite

Carrier frequencies, holomorphy and unwinding

Journal Article SIAM Journal on Mathematical Analysis Open Access Cite