Theories and Applications of Non-Contact Sleep Monitoring using Microwave Doppler Radar

University of Technology Sydney. Faculty of Engineering and Information Technology.Obstructive sleep apnea (OSA) is a common and potentially lethal sleep disorder affecting at least 4% of adult males and 2% of adult females worldwide. Early detection, treatment and continuous monitoring of OSA are extremely important as it may reduce the risks associated with cardiovascular comorbidities. Polysomnography (PSG) is the gold-standard to diagnose OSA, however there are limitations, such as its unsuitability for long-term continuous monitoring. The Thesis is a response to the demands for the non-contact sleep monitoring systems. The demands arise due to the limitations of the PSG system, the importance of early screening for OSA, the need for long-term continuous monitoring and the concern with respect to patient discomfort when using the gold-standard PSG system. The research presented in the Thesis are the novel theories, real-life applications and the results of the non-contact sleep monitoring using the non-contact microwave Doppler radar, including the “non-stationary” and “non-direct facing” subjects’ measurements in the complex sleep environment. The novel theories that the Thesis contributes to the field of non-contact sleep monitoring are: 1. Relative Demodulation – a novel theory and technique for real-time demodulation of the subject’s chest or abdomen periodic motions using non-contact microwave Doppler radar. 2. Pulmonary Ventilation Mathematical Model – a novel mathematical model of the physiological pulmonary ventilation that enables the estimation of tidal volume using non-contact microwave Doppler radar. 3. External Ventilation Mathematical Model – a novel mathematical model of the physiological external ventilation that enables the estimation of oxygen saturation using non-contact microwave Doppler radar. 4. 3-Dimensional Feature Representation and Extraction – a novel theory and technique that represents and extracts features in 3-dimensional space. This technique, when combine with the artificial neural networks (ANN) will enable the predictions of body orientations and oxygen saturation using non-contact microwave Doppler radar. The novel non-contact sleep monitoring real-life applications and results that the Thesis contributes to the field of non-contact sleep monitoring are: 1. Respiratory rate – achieves 91.53% accuracy with median error of ±1.30 breaths/min. 2. Heart rate – achieves 91.28% accuracy with median error of ±6.20 beats/min. 3. Tidal volume – achieves 83.13% accuracy with median error of 57.32 milliliters. 4. Body orientations – achieve high correct classification rate of 99.9%. The misclassification is at a negligible rate of 0.1%. 5. Oxygen saturation – achieves correlation coefficient of 0.92 and the 95% limits of agreement is ±2.7 (% oxygen saturation). The contributions of the novel theories, real-life applications and the results presented in the Thesis demonstrated a good level of accuracies. The potential applications include non-contact sleep early screening and/or continuous monitoring of the respiratory and heart rates, tidal volume, body orientations and saturation oxygen during sleep. This can be use in homes, hospitals, primary care sectors, nursing home facilities and/or sleep laboratories

The causal relationships between components of customer-based brand equity for a destination: Evidence from South Korean tourists in Danang city, Vietnam

The main purpose of this study is to examine the causal relationships between components of customer-based brand equity for a tourist destination. We have collected data from 252 South Korean tourists in Danang City and tested some hypotheses by applying structural equation modeling (SEM). Results show that: (1) destination brand awareness has a significant and positive effect on destination brand image, but not on destination perceived quality and destination brand loyalty; (2) destination brand image has positive and direct influences on destination perceived quality and destination brand loyalty; and (3) destination perceived quality has significant positive impacts on destination brand loyalty. Lastly, these findings have managerial implications for decision makers

Doppler radar-based non-contact health monitoring for obstructive sleep apnea diagnosis: A comprehensive review

Today’s rapid growth of elderly populations and aging problems coupled with the prevalence of obstructive sleep apnea (OSA) and other health related issues have affected many aspects of society. This has led to high demands for a more robust healthcare monitoring, diagnosing and treatments facilities. In particular to Sleep Medicine, sleep has a key role to play in both physical and mental health. The quality and duration of sleep have a direct and significant impact on people’s learning, memory, metabolism, weight, safety, mood, cardio-vascular health, diseases, and immune system function. The gold-standard for OSA diagnosis is the overnight sleep monitoring system using polysomnography (PSG). However, despite the quality and reliability of the PSG system, it is not well suited for long-term continuous usage due to limited mobility as well as causing possible irritation, distress, and discomfort to patients during the monitoring process. These limitations have led to stronger demands for non-contact sleep monitoring systems. The aim of this paper is to provide a comprehensive review of the current state of non-contact Doppler radar sleep monitoring technology and provide an outline of current challenges and make recommendations on future research directions to practically realize and commercialize the technology for everyday usage

Homogénéisation numérique à l'aide de modèles prior de la raideur mésoscopique : identification et validation

L'homogénéisation numérique des microstructures aléatoires requiert la résolution du problème du correcteur sur un grand nombre de réalisations. L'effort de calcul numérique est plus marqué lorsque la géométrie des microstructures est complexe et le contraste mécanique entre phases est considérable (typiquement > 100). Dans les deux cas, la finesse de la grille de discrétisation implique un coût de calcul très important. Récemment, Bignonnet et coll. [1] ont proposé une technique de filtrage permettant d'introduire des microstructures équivalentes (appelées mésostructures). Une des caractéristiques essentielles de cette approche est que les propriétés macroscopiques de la mésostructure coïncident avec celles de la microstructure sous-jacente; le filtrage réduit par ailleurs les fluctuations locales de raideur (voir Fig. 1). Par conséquent, une grille plus grossière peut être utilisée dans la résolution du problème du correcteur. En faisant varier la taille caractéristique H du filtre, on obtient un continuum de représentations pour le tenseur d'élasticité, de l'échelle microscopique jusqu'à l'échelle macroscopique. On s'intéresse dans ce travail à la calibration et la validation d'un modèle prior [5] pour représenter la raideur mésoscopique obtenue par la technique de filtrage de Bignonnet et coll. [1]. Dans la première partie, nous décrivons la génération et l'analyse statistique des raideurs mésoscopiques d'un modèle de microstructure de type matrice-inclusions (sphériques). Ensuite, dans la deuxième partie nous introduisons un modèle prior basé sur le principe du maximum d'entropie. Nous montrons que le modèle peut être calibré soit par les estimateurs statistiques, soit par la méthode du maximum de vraisemblance dans la troisième partie. En fin, nous décrivons la validation du modèle prior et des méthodes d'identification mise en œuvre en comparant certains grandeurs d'intérêt mésoscopiques et macroscopiques

Stress-gradient materials: an analytical exploration

International audienceA new stress-gradient elasticity theory has recently been proposed by Forest & Sab (Mech. Res. Comm. 40:16--25, 2012), and further analyzed by Forest, Legoll & Sab (J. Elas., submitted). This new model makes the assumption that the complementary energy is a function of the local stress and (the deviatoric part of) its first gradient. Its derivation (including boundary conditions) relies on a rigorous variational approach. However, the resulting set of equations is rather complex in general. In order to better understand this model, it is proposed as a first step to consider a subclass of stress-gradient materials, assuming material isotropy and restricting to only one internal material length.In this talk, we propose an analytical exploration of this simplified model. We will produce the closed-form solution to Eshelby's spherical inhomogeneity problem. From the analysis of the corresponding local fields, we will show that stress- and strain-gradient elasticity theories are not in duality, as one would be tempted to think.This elementary solution will then be used to extend the micromechanical model of Mori and Tanaka to stress gradient materials. In particular, we will show that (contrary to strain-gradient materials) a decrease of the internal material lenth tends to stiffen the material