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Noise Cancellation

Yi-Quan Zou, Ling-Na Wu, Qi Liu, Xin-Yu Luo, Shuai-Feng Guo, Jia-Hao Cao, Meng Khoon Tey, Li You
Interferometry is a paradigm for most precision measurements. Using N uncorrelated particles, the achievable precision for a two-mode (two-path) interferometer is bounded by the standard quantum limit (SQL), [Formula: see text], due to the discrete (quanta) nature of individual measurements. Despite being a challenging benchmark, the two-mode SQL has been approached in a number of systems, including the Laser Interferometer Gravitational-Wave Observatory and today's best atomic clocks. For multimode interferometry, the SQL becomes [Formula: see text] using M modes...
June 1, 2018: Proceedings of the National Academy of Sciences of the United States of America
Hossein Emami, Mohammadreza Hajihashemi, Sayed Ehsan Alavi, Abu Sahmah Mohd Supaat
A microwave photonics instantaneous frequency measurement receiver was conceived and practically demonstrated. The system is based on phase modulation inside a Sagnac loop and therefore needs no bias voltage, resulting in no DC bias drifts. The system provides a DC output whose amplitude is a function of input signal frequency, and thus no high-frequency photo-detector is required. Furthermore, the system exhibits a very good sensitivity without the aid of any sort of electrical noise cancellation techniques, such as lock-in amplification...
May 15, 2018: Optics Letters
M Ghahramanifar, M Haghani, A Ghadimi Moghadam, A K Ghadimi Moghadam
As regards the significant role of stethoscopes in the diagnosis of congenital and adventitious heart diseases and prevention of irreparable complications of these diseases, the quality of hearing sound of these stethoscopes by a physician has a significant impact on the disease diagnosis. This device plays an important role in the early diagnosis of congenital heart and respiratory diseases and provides this feasibility since birth. Also, the importance of this device performance in the diagnosis of heart, cardiovascular and respiratory diseases at different age periods is not a secret...
March 2018: Journal of Biomedical Physics & Engineering
Linda L Chlan, Annette Heiderscheit, Debra J Skaar, Marjorie V Neidecker
OBJECTIVES: Music intervention has been shown to reduce anxiety and sedative exposure among mechanically ventilated patients. Whether music intervention reduces ICU costs is not known. The aim of this study was to examine ICU costs for patients receiving a patient-directed music intervention compared with patients who received usual ICU care. DESIGN: A cost-effectiveness analysis from the hospital perspective was conducted to determine if patient-directed music intervention was cost-effective in improving patient-reported anxiety...
May 4, 2018: Critical Care Medicine
Hyunwoo Lee, Mincheol Whang
Cardiac activity has been monitored continuously in daily life by virtue of advanced medical instruments with microelectromechanical system (MEMS) technology. Seismocardiography (SCG) has been considered to be free from the burden of measurement for cardiac activity, but it has been limited in its application in daily life. The most important issues regarding SCG are to overcome the limitations of motion artifacts due to the sensitivity of motion sensor. Although novel adaptive filters for noise cancellation have been developed, they depend on the researcher’s subjective decision...
May 1, 2018: Sensors
Ken Kashiwagi, Yoshiaki Nakajima, Masato Wada, Sho Okubo, Hajime Inaba
In multi-branch combs, the comb outputs from the branches suffer from different fiber noises, which often limit the uncertainty of the combs referring a highly-stable optical frequency. To overcome this limitation, we introduced fiber noise difference cancellation to multi-branch fiber combs. We detected and phase-locked the beat notes between the branch outputs and a common 1542 nm continuous wave laser. A piezo-electric transducer-based fiber stretcher was installed in each branch except for the branch used as the cancellation reference...
April 2, 2018: Optics Express
Kevin Audo, Abdelkrim El Amili, Mehdi Alouini
A theoretical model describing the dynamical behavior of dual-frequency solid-state lasers including a buffer reservoir (BR) is presented. It relies on the introduction of two additional coupled rate equations describing the interaction of the two laser modes with the BR. The relative intensity noise is derived by taking into account the fluctuations of both pump intensity and intra-cavity photons. This modelling approach accurately predicts the experimental noise spectra obtained with an Er,Yb:glass dual-frequency laser implemented in different cavity architecture configurations...
April 2, 2018: Optics Express
Hui Liu, Gregory Gredat, Syamsundar De, Ihsan Fsaifes, Aliou Ly, Rémy Vatré, Ghaya Baili, Sophie Bouchoule, Fabienne Goldfarb, Fabien Bretenaker
An ultra-low intensity and beatnote phase noise dual-frequency vertical-external-cavity surface-emitting laser is built at telecom wavelength. The pump laser is realized by polarization combining two single-mode fibered laser diodes in a single-mode fiber, leading to a 100% in-phase correlation of the pump noises for the two modes. The relative intensity noise is lower than -140  dB/Hz, and the beatnote phase noise is suppressed by 30 dB, getting close to the spontaneous emission limit. The role of the imperfect cancellation of the thermal effect resulting from unbalanced pumping of the two modes in the residual phase noise is evidenced...
April 15, 2018: Optics Letters
B Rauf, M C Vélez López, P Thoumany, M Pizzocaro, D Calonico
The distribution of ultra-narrow linewidth laser radiation is an integral part of many challenging metrological applications. Changes in the optical pathlength induced by environmental disturbances compromise the stability and accuracy of optical fibre networks distributing the laser light and call for active phase noise cancellation. Here we present a laboratory scale optical (at 578 nm) fibre network featuring all polarisation maintaining fibres in a setup with low optical powers available and tracking voltage-controlled oscillators implemented...
March 2018: Review of Scientific Instruments
Xiaofeng Yi, Jian Zhang, Tiehu Fan, Baofeng Tian, Chuandong Jiang
Magnetic resonance sounding (MRS) is a novel geophysical method to detect groundwater directly. By applying this method to underground projects in mines and tunnels, warning information can be provided on water bodies that are hidden in front prior to excavation and thus reduce the risk of casualties and accidents. However, unlike its application to ground surfaces, the application of MRS to underground environments is constrained by the narrow space, quite weak MRS signal, and complex electromagnetic interferences with high intensities in mines...
March 13, 2018: Sensors
Jokhakar Jignesh, Arthur Lowery, Bill Corcoran
We propose optical injection locking (OIL) to enable compensation of the inter-channel nonlinear phase noise, which is dominated by cross-phase modulation (XPM). In this paper, injection locking is used to create a local oscillator for a homodyne receiver from a residual carrier. The locking is fast enough to follow XPM-phase distortion, but slow enough to reject the signal bands, which are spaced slightly away from the pilot. The homodyne receiver thus partially cancels XPM, as it is common to the signals and the pilot...
March 5, 2018: Optics Express
Kevin Audo, Mehdi Alouini
An absorption mechanism based on second-harmonic generation (SHG) is successfully implemented as a buffer reservoir in a solid-state Er,Yb:Glass laser emitting at the telecom wavelength. We show that a slight absorption mechanism based on SHG rate conversion of 0.016% using a beta barium borate crystal enables the canceling out of the excess intensity noise at the relaxation oscillation frequency, i.e., 35 dB reduction, as well as canceling the amplified spontaneous emission beating at the free spectral range resonances of the laser lying in the gigahertz range...
March 1, 2018: Applied Optics
Mohammad Tariqul Islam, Sk Tanvir Ahmed, Ishmam Zabir, Celia Shahnaz, Shaikh Anowarul Fattah
Photoplethysmographic (PPG) signal is getting popularity for monitoring heart rate in wearable devices because of simplicity of construction and low cost of the sensor. The task becomes very difficult due to the presence of various motion artefacts. In this study, an algorithm based on cascade and parallel combination (CPC) of adaptive filters is proposed in order to reduce the effect of motion artefacts. First, preliminary noise reduction is performed by averaging two channel PPG signals. Next in order to reduce the effect of motion artefacts, a cascaded filter structure consisting of three cascaded adaptive filter blocks is developed where three-channel accelerometer signals are used as references to motion artefacts...
February 2018: Healthcare Technology Letters
André Guedes, Rita Macedo, Gerardo Jaramillo, Susana Cardoso, Paulo P Freitas, David A Horsley
Advances in the magnetic sensing technology have been driven by the increasing demand for the capability of measuring ultrasensitive magnetic fields. Among other emerging applications, the detection of magnetic fields in the picotesla range is crucial for biomedical applications. In this work Picosense reports a millimeter-scale, low-power hybrid magnetoresistive-piezoelectric magnetometer with subnanotesla sensitivity at low frequency. Through an innovative noise-cancelation mechanism, the 1/f noise in the MR sensors is surpassed by the mechanical modulation of the external magnetic fields in the high frequency regime...
March 6, 2018: Sensors
Elizabeth A Kelly, Michael E Stadler, Steven Nelson, Christina L Runge, David R Friedland
OBJECTIVE: To determine the feasibility of audiometric screening with tablet-based applications in typical clinic locations: examination room and clinic waiting area. STUDY DESIGN: A randomized prospective study. SETTING: Tertiary referral center. PATIENTS: Participants included 107 adult patients referred for audiometric testing to assess hearing loss. INTERVENTION: Each patient completed standard audiometry testing and one of three tablet-based audiometric applications that included pure-tone air conduction testing...
April 2018: Otology & Neurotology
Wei Du, Jun Jia, J F Chen, Z Y Ou, Weiping Zhang
Absolute sensitivity is measured for the phase measurement in an SU(1,1) type interferometer, and the results are compared to that of a Mach-Zehnder interferometer operated under the condition of the same intra-interferometer intensity. The interferometer is phase locked to a point with the largest quantum noise cancellation, and a simulated phase modulation is added in one arm of the SU(1,1) interferometer. Both the signal and noise level are estimated at the same frequency range, and we obtained 3 dB improvement in sensitivity for the SU(1,1) interferometer over the Mach-Zehnder interferometer...
March 1, 2018: Optics Letters
Daniel Hamacher, Franziska Schley, Karsten Hollander, Astrid Zech
Auditory information affects sensorimotor control of gait. Noise or active noise cancelling alters the perception of movement related sounds and, probably, gait stability. The aim of the current study was to evaluate the effects of noise cancelling on gait stability. Twenty-five healthy older subjects (70 ± 6 years) were included into a randomized cross-over study. Gait stability (largest Lyapunov exponent) in normal overground walking was determined for the following hearing conditions: no manipulation and active noise cancelling...
April 2018: Human Movement Science
Phoebe E Riley, Douglas S Ruhl, Macario Camacho, Anthony M Tolisano
Objective The cochlear implant (CI) improves quality of life for people who are severely and profoundly deafened, allowing implantees to perceive speech at levels similar to those of individuals with normal hearing. However, patients with CIs generally report a reduced appreciation of music after implantation. We aimed to systematically review the English-language literature for studies evaluating music enjoyment and perception among adult patients with CIs. Data Sources A systematic review of PubMed/MEDLINE, Scopus, Embase, and the Cochrane Library...
February 1, 2018: Otolaryngology—Head and Neck Surgery
Jie Yang, Zhiguo Gui, Liyuan Zhang, Pengcheng Zhang
PURPOSE: To reduce computation and decrease planning time with little or no loss in plan quality compared to the column-generation-based (cg) method, a simple method of aperture generation based on threshold segmentation (agts) is proposed. METHODS: The proposed agts strategy consists of two steps. First, a fuzzy controller is used for noise cancellation; then, new apertures are added using the threshold segmentation algorithm. We tested the proposed method on seven prostate tumor cases using the computational environment for radiotherapy research algorithms for the dose calculations and compared the results with those obtained by generating the plan aperture using the cg method...
April 2018: Medical Physics
Sevgi Gokce Kafali, Tolga Çukur, Emine Ulku Saritas
PURPOSE: DWI suffers from low SNR when compared to anatomical MRI. To maintain reasonable SNR at relatively high spatial resolution, multiple acquisitions must be averaged. However, subject motion or involuntary physiological motion during diffusion-sensitizing gradients cause phase offsets among acquisitions. When the motion is localized to a small region, these phase offsets become particularly problematic. Complex averaging of acquisitions lead to cancellations from these phase offsets, whereas magnitude averaging results in noise amplification...
February 9, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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