A comprehensive study of the effect of a wide range of controlled human subject motion on Photoplethysmographic signals is reported. The investigation includes testing of two separate groups of 5 and 18 subjects who were asked to undertake set exercises whilst simultaneously monitoring a wide range of physiological parameters including Breathing Rate, Heart Rate and Localised Blood Pressure using commercial clinical sensing systems. The unique finger mounted PPG probe equipped with miniature three axis accelerometers for undertaking this investigation was a purpose built in-house version which is designed to facilitate reproducible application to a wide range of human subjects and the study of motion. The subjects were required to undertake several motion based exercises including standing, sitting and lying down and transitions between these states. They were also required to undertake set arm movements including arm-swinging and wrist rotation. A comprehensive set of experimental results corresponding to all motion inducing exercises have been recorded and analysed including the baseline (BL) value (DC component) and the amplitude of the oscillation of the PPG. All physiological parameters were also recorded as a simultaneous time varying waveform. The effects of the motion and specifically the localised Blood Pressure (BP) have been studied and related to possible influences of the Autonomic Nervous System (ANS) and hemodynamic pressure variations. It is envisaged that a comprehensive study of the effect of motion and the localised pressure fluctuations will provide valuable information for the future minimisation of motion artefact effect on the PPG signals of this probe and allow the accurate assessment of total haemoglobin concentration which is the primary function of the probe.
A multi-wavelength switchable C-band erbium-doped fiber laser based on a hybrid comb filter composed of a Sagnac loop and Mach–Zehnder interferometer (MZI) is designed and experimentally demonstrated. In the designed ring cavity fiber laser, the MZI is composed of bi-tapered single-mode fiber fabricated by etching with hydrofluoric acid. In the experiment, the wavelength intervals in the comb spectra of the Sagnac loop and MZI are 3.4 and 18.8 nm, respectively, and by combining the Sagnac loop and MZI, measurements of the hybrid comb spectrum are obtained. When the pump power is 91 mW, lasing occurs at 1529.2 nm. Adjustment of the variable attenuator (VA) can provide 1541.9 and 1558.6 nm single-wavelength switchable lasers, for which the maximum peak power difference is less than 3.59 dB, the signal-to-noise ratio (SNR) exceeds 19.25 dB, and the peak power fluctuation is less than 0.34 dB over a 30 min scan time at 26 °C. For dual-wavelength switchable laser emission, four different sets of wavelengths can be realized, and the SNR exceeds 15.57 dB with power fluctuations of less than 1.6 dB, under the same monitoring conditions. By further adjusting the VA, stable and tunable triple-wavelength lasing is also realizable; under these conditions, the SNR exceeds 15.02 dB and the power fluctuation is less than 0.91 dB. Furthermore, four- and five-wavelength lasing can also be achieved by adjusting the VA again, with SNRs exceeding 19.05 and 14.98 dB, respectively.
The collection of photoplethysmography (PPG) signals from optical based sensor probe has been used extensively for the monitoring of heart rate (HR), respiration rate and oxygen saturation (SpO 2 ). Prior research by the Optical Fibre Sensor Research Group has extended the information provided by PPG based devices from monitoring HR and SpO 2 to include total haemoglobin concentration (Hb). Research presented here demonstrates that PPG signals are severely influenced by the autonomic nervous system (ANS) variations induced by physiological events, such as yawning and coughing. Using a finger sensor probe with an embedded accelerometer, further investigation demonstrates that PPG based measurements including HR, SpO 2 and Hb are strongly degraded by ANS both during a) movement of body position and b) physiological variation.
During plasma disruptions (PDs), transient eddy currents are induced in the HL-2M vacuum vessel (VV) which is a D-shaped, double thin-wall structure. Under the circumstance of high magnetic field, the resulting electromagnetic (EM) forces during PDs are large and the dynamic response of related structures may be violent. In this complicated EM circumstance, the EM-mechanical coupling effect may also have a great influence on the dynamic response of VV structure. In this paper, the EM field and structural dynamic response of HL-2M VV during PDs are simulated by adopting a numerical code of the Lagrangian approach. The Lagrangian approach is on the basis of the Maxwell equations in the Lagrangian description, which treats the coupling behavior of magnetic damping effect without explicitly using the velocity term. This approach can be easily applied to actual structures by updating FEM meshes and reforming coefficient matrices before calculating EM field at each time step. In this work, the disruption plasma currents of operating conditions are simulated by using the DINA code and then the dynamic responses of displacements and stresses of the VV of HL-2M are obtained for both cases with and without considering the coupling effect. The numerical results show that stresses under the disruptions (MD and VDE) are not significant and the coupling effect does not significantly affect the peak dynamic response for the HL-2M problem.
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