To enhance the accuracy of phase measurement and to prevent tracking errors, it is crucial to effectively read the multi-frequency signal in space gravitational wave detection. In this paper, a novel signal acquisition method called the multi-frequency acquisition algorithm is proposed and implemented. Different from the traditional single-frequency acquisition, the signal characteristics of amplitude and frequency are both considered to better distinguish different frequency components. A phasemeter integrated with the acquisition method and narrow-bandwidth digital phase-locked loop is constructed for the method test and verification. The results show that the multi-frequency acquisition unit can capture all the frequencies of an input signal in several milliseconds. The precision is better than ±200 Hz under a low SNR (signal-to-noise ratio) of 0 dB. The phase noise can reach 2 µrad/Hz1/2 in the frequency range of 0.1-1 Hz and satisfy the requirement of the space gravitational wave detection in all frequency ranges.
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Sci Adv
December 2024
McCaig Institute for Bone and Joint Health, University of Calgary, 3280 Hospital Drive NW, Calgary T2N 4Z6, Canada.
Mechanical unloading causes bone loss, but it remains unclear whether disuse-induced changes to bone microstructure are permanent or can be recovered upon reloading. We examined bone loss and recovery in 17 astronauts using time-lapsed high-resolution peripheral quantitative computed tomography and biochemical markers to determine whether disuse-induced changes are permanent. During 6 months in microgravity, resorption was threefold higher than formation.
View Article and Find Full Text PDFSensors (Basel)
December 2024
Space Environmental Load Engineering Center, Lanzhou Institute of Physics, Lanzhou 730000, China.
Sensors (Basel)
November 2024
Center for Gravitational Wave Experiment, National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
Since Einstein's prediction regarding the existence of gravitational waves was directly verified by the ground-based detector Advanced LIGO, research on gravitational wave detection has garnered increasing attention. To overcome limitations imposed by ground vibrations and interference at arm's length, a space-based gravitational wave detection initiative was proposed, which focuses on analyzing a large number of waves within the frequency range below 1 Hz. Due to the weak signal intensity, the TMs must move along their geodesic orbit with a residual acceleration less than 10 m/s/Hz.
View Article and Find Full Text PDFEur J Neurosci
January 2025
Faculty of Psychology, Otemon Gakuin University, Ibaraki, Osaka, Japan.
Accurate perception of the orientation of external objects relative to the body, known as egocentric spatial orientation, is fundamental to performing action. Previously, we found via behavioural and magnetic resonance imaging voxel-based morphometry studies that egocentric spatial orientation is strongly distorted when the whole body is tilted with respect to gravity, and that the magnitude of this perceptual distortion is correlated with the grey matter volume of the right middle occipital gyrus (rMOG). In the present study, we further validated the association between the neural processing in the rMOG and the perceptual distortion by transiently suppressing neural activity in this region using low-frequency repetitive transcranial magnetic stimulation (rTMS) and evaluating the consequent effect on perceptual distortion.
View Article and Find Full Text PDFMil Med
December 2024
Clinical and Operational Space Medicine Innovation Consortium (COSMIC), 59th Medical Wing, Lackland Air Force Base, TX 78236, USA.
Introduction: Commercial off-the-shelf (COTS) intravenous fluid (IVF) containers contain residual air, introducing the risk of venous air embolism (VAE). Venous air embolism occurs when air displaces blood flow in vasculature. The danger from residual air is often negligible in terrestrial settings, where gravitational forces generate buoyancy, pushing residual air to the top of the IVF container.
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