It can be life-saving to monitor the respiratory rate (RR) even for healthy people in real-time. It is reported that the infected people with coronavirus disease 2019 (COVID-19), generally develop mild respiratory symptoms in the early stage. It will be more important to continuously monitor the RR of people in nursing homes and houses with a non-contact method. Conventional, contact-based, methods are not suitable for long-term health monitoring especially in-home care services. The potentials of wireless radio signals for health care applications, such as fall detection, etc., are examined in literature. In this paper, we focus on a device-free real-time RR monitoring system using wireless signals. In our recent study, we proposed a non-contact RR monitoring system with a batch processing (delayed) estimation method. In this paper, for real-time monitoring, we modify the standard joint unscented Kalman filter (JUKF) method for this new and time-critical problem. Due to the nonlinear structure of the RR estimation problem with respect to the measurements, a novel modification is proposed to transform measurement errors into parameter errors by using the hyperbolic tangent function. It is shown in the experiments conducted with the real measurements taken using healthy volunteers that the proposed modified joint unscented Kalman filter (ModJUKF) method achieves the highest accuracy according to the windowing-based methods in the timevarying RR scenario. It is also shown that the ModJUKF not only reduces the computational complexity approximately 8.54% but also improves the accuracy 36.7% with respect to the standard JUKF method. INDEX TERMS Unscented Kalman filter, joint unscented Kalman filter, respiratory rate tracking, devicefree, vital signs, health monitoring, radio signals.

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Continuous monitoring of respiratory rate (cycle) during sleep for diseases such as sleep apnea and sudden infant death syndrome (SIDS) can be lifesaving. Wireless radio communications signals are everywhere and can be harnessed for contactless monitoring of the respiratory rates. The amplitude of the received signal strength changes periodically depending on the exhalation and inhalation of the subject. In this paper, subspace-based multiple signal classification (MUSIC) algorithm is applied to estimate the respiratory rate for better results. The proposed method and the other power spectral density (PSD) methods for respiratory estimations are compared with the real laboratory measurements. It is demonstrated that the proposed method estimates the respiratory rate with high accuracy and outperforms the other PSD-based methods which are commonly used in the literature.

An advanced, high-effectiveness film cooling design, the antivortex hole (AVH) has been investigated by several research groups and shown to mitigate or counter the vorticity generated by conventional holes and increase film effectiveness at high blowing ratios and low freestream turbulence levels. The effects of increased turbulence on an AVH geometry were previously investigated in a preliminary steady computational fluid dynamics (CFD) study by Hunley et al. on the film effectiveness and net heat flux reduction (NHFR) at high blowing ratio. The current paper presents the results of an extended numerical parametric study, which attempts to separate the effects of turbulence intensity and length scale on film cooling performance of the AVH concept at high blowing ratio (2.0) and density ratio (2.0). In this extended study, steady Reynolds-averaged Navier–Stokes (RANS) analysis was performed with turbulence intensities of 5, 10, and 20% and length scales based on cooling hole diameter of Λx/dm = 1, 3, and 6. Increasing turbulence intensity was shown to increase the centerline, span-averaged, and area-averaged adiabatic film cooling effectiveness and NHFR. Larger turbulent length scales in the steady RANS analysis were shown to have little to no effect on the centerline, span-averaged, and area-averaged adiabatic film cooling effectiveness and NHFR at lower turbulence levels, but moderate effect at the highest turbulence levels investigated. Heat transfer results were in good agreement with the findings from adiabatic cases from previous work. Unsteady RANS results also provided supplementary flow visualization for the AVH film cooling flow under varying turbulence levels.

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