1,031 research outputs found
Optomechanical cooling and inertial sensing at low frequencies
An inertial sensor design is proposed in this paper to achieve high
sensitivity and large dynamic range in the sub-Hz frequency regime. High
acceleration sensitivity is obtained by combining optical cavity readout
systems with monolithically fabricated mechanical resonators. A
high-sensitivity heterodyne interferometer simultaneously monitors the test
mass with an extensive dynamic range for low-stiffness resonators. The
bandwidth is tuned by optical feedback cooling to the test mass via radiation
pressure interaction using an intensity-modulated laser. The transfer gain of
the feedback system is analyzed to optimize system parameters towards the
minimum cooling temperature that can be achieved. To practically implement the
inertial sensor, we propose a cascaded cooling mechanism to improve cooling
efficiency while operating at low optical power levels. The overall system
layout presents an integrated design that is compact and lightweight
Optomechanical lasers for inertial sensing
We have developed an inertially sensitive optomechanical laser by combining a
Vertical-External-Cavity Surface-Emitting Laser with a monolithic fused silica
resonator. By placing the external cavity mirror of the VECSEL onto the
optomechanical resonator test mass, we create a sensor where external
accelerations are directly transcribed onto the lasing frequency. We developed
a proof-of-principle laboratory prototype and observe test mass oscillations at
the resonance frequency of the sensor through the VECSEL lasing frequency, 4.18
+/- .03 Hz. In addition, we set up an ancillary heterodyne interferometer to
track the motion of the mechanical oscillator's test mass, observing a
resonance of 4.194 +/- 0.004 Hz. The interferometer measurements validate the
VECSEL results, confirming the feasibility of using optomechanical lasers for
inertial sensing
Neonatal Abstinence Syndrome and Infant Hearing Assessment: A Kids’ Inpatient Database Review
Objective: Neonatal abstinence syndrome (NAS) has become an epidemic. This study assesses documented rates of failed newborn hearing screening (NBHS) or hearing loss diagnosis (HL) in NAS infants, and sociodemographic factors associated with abnormal inpatient hearing results.
Methods: The 2016 HCUP/KID national database was used to identify a weighted sample of infants with failed NBHS/HL during birth hospitalization. Independent variables included diagnoses of NAS/in-utero opioid exposure, HL risk factor presence and sociodemographic data. Univariate analyses and multivariate logistic regression were used to determine associations between NAS and abnormal hearing assessment.
Results:NAS infants had lower odds ratio (OR) of documented failed NBHS (OR=0.76, p
Conclusion: NAS children have lower rates of inpatient documented failed NBHS and higher rates of HL diagnosis. The complex medical care of these infants could complicate NBHS, documentation, and subsequent follow-up. Certain sociodemographic factors result in a higher risk of hearing loss
Optomechanical accelerometers for geodesy
We present a novel optomechanical inertial sensor for low frequency
applications and corresponding acceleration measurements. This sensor has a
resonant frequency of 4.7Hz, a mechanical quality factor of 476k, a test mass
of 2.6 gram, and a projected noise floor of approximately 5E-11 m s-2. per
root-Hz at 1Hz. Such performance, together with its small size, low weight,
reduced power consumption, and low susceptibility to environmental variables
such as magnetic field or drag conditions makes it an attractive technology for
future geodesy missions. In this paper, we present an experimental
demonstration of low-frequency ground seismic noise detection by direct
comparison with a commercial seismometer, anda data analysis algorithms for the
identification, characterization, and correction of several noise sources
Development of a Coherent Doppler Lidar for Precision Maneuvering and Landing of Space Vehicles
A coherent Doppler lidar has been developed to address NASAs need for a high-performance, compact, and cost-effective velocity and altitude sensor onboard its landing vehicles. Future robotic and manned missions to planetary bodies require precise ground-relative velocity vector and altitude data to execute complex descent maneuvers and safe, soft landing at a pre-designated site. This lidar sensor, referred to as a Navigation Doppler Lidar, meets the required performance of landing missions while complying with vehicle size, mass, and power constraints. Operating from over five kilometers altitude, the lidar obtains velocity and range precision measurements with 2 cm/sec and 2 meters, respectively, dominated by the vehicle motion. After a series of flight tests onboard helicopters and rocket-powered free-flyer vehicles, the Navigation Doppler Lidar is now being ruggedized for future missions to various destinations in the solar system
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